It's a bit of both really. It's definitely, definitely not bandwagon jumping because Achtung Baby, Zooropa and Passengers exist before it. You can't have 3 albums of mucking around inch by inch with straight out electronica and/or simply 'rock with hips', and then suddenly claim on the 4th album that it's just a cheap stunt. It's a different sound, but post the lighter euro-electro Zooropa, the heavier and darker themes of those Pop songs demanded that heavier stressful, pained sound on Pop. That the Chemical Bros etc were the sound of the moment is fine, it's not like U2 hadn't danced around the sound of the moment at several points earlier, it's too their credit that they've never been afraid to incorporate what is new around them to suit their needs at the time, and it's understandable that whatever it is you are listening to a lot of will either creep in subtly or utterly dominate the ideas swirling in your head.
It's not wildly experimental, and I personally argue against that tag all the time. I don't think there's much in U2's catalogue that is greatly more experimental than anything else before or after it. I don't really see the difference between Edge mucking around with euro electro-beats on Zooropa, and Edge mucking around with the blues on R&H. Or U2 using Howie B and a heavy electro thump to drag their songs down into the manic traffic jam on Pop, and U2 using Brian Eno and some synthesized backing to take their songs up into the open stratosphere on The Unforgettable Fire. Influence and experimentation is relative, and really in the end with U2 it's all relatively surface level, whether it's messing with a genre, or messing with a certain technology, or messing with a current sonic influence. I mean, tell me what the huge difference between Bullet the Blue Sky and Mofo is? There's none really - from the driving bass line, to the drum snaps, to Bono growling, to the guitar screams. Re-invention is U2's game, not wild experimentation.
If it's 'daring' and 'brave' it is for the exact same reasons ATYCLB is. Read Bono's quotes leading into and promoting Pop, and read them leading into and promoting ATYCLB. They are essentially the same: Rock is stale, we want to reclaim it. Stop staring at your toes and pretending you hate it. Think big and ambitious and bright and bold. Take big songs and send them global. They thought then that there was a niche there for them to claim. That the way to save rock was to reinvent it. Later with ATYCLB they took the other path - don't try for something new to take on the world, reintroduce the world to it the way it is at it's root goodness.
It's why now Bono says that if you just imagine Discotheque was a huge global hit, you can see how the rest of Pop and their ambitions for Pop fall into place. I agree. I also always say that I think Pop is no complete disaster, that it's actually only within an inch of being as perfect a U2 album as they've ever done. Some think the thing needs a complete overhaul or should never have even been attempted, I think it simply needs an extra couple of weeks of more careful editing and mixing and that it's biggest curse came long before the first note of it was heard. The story doing the rounds long before that U2 are making a dance/techno album, and the fact that U2 were releasing anything in 1997 which such open and naked ego and ambition - an absolutely toxic year to be the biggest band in the world attempting the biggest album in the world backed by the biggest tour in the world - were setting them up for disaster. It's another thing they corrected pre-ATYCLB. I think with Pop it's those three key elements: Take the extra month to fix it's glitches. The songs do not need the reworking they got for Best Of's etc, they just need 10% more effort in the production/mixing/editing. Shoot down any dance/techno/wildly weird shit early. Talk it up as a rock record to counter that if you must. Upon release, take it softly softly and let the music speak for itself. No Kmart press conference. No dicky Discotheque clips. No ego. Do as with ATYCLB - take the songs to some small clubs for a few gigs. Focus it on the music. Then if/once Discotheque was that global hit - NOW start talking all your world domination, reclaim rock, biggest band in the world shit. NOW announce this ridiculously oversized tour from the lingerie department of Kmart. Just a few small changes here and there and Pop (and Popmart) would have had a far softer landing, a greatly different reception, and an utterly opposite place in their history.
So yes, after going off the path a bit there, in summary: It was daring and brave because it was the first time perhaps since Boy that U2 walked into a studio and didn't just want to make a great album that in some way propels themselves forward, be it career wise or musical growth wise or whatever, but actually expected to walk into that studio, take rock itself by the balls and walk out the otherside with something that changes the face of it forever. It was with the same naivety and a sort of innocence that they had when they started out, but mixed with the confidence of having kicked arse at everything in between. Especially immediately beforehand where they'd destroyed and rebuilt themselves completely, again to stunning success. It created the ego and arrogance that ultimately is what led to Pops downfall. The ambition and intent, and what is actually there on the disc, is perfectly admirable. It IS identical to ATYCLB in that regard. Whether musically they were ever on the right path or not, we'll never know. A large chunk of rock definitely has taken a danceable electro inspired or embedded influence in this decade - they were definitely right about that, and the colour and ambition is most certainly back (I mean, you couldn't imagine any other 90s generated band fronting the Popmart stage, but there are loads today - eg the Killers - who match an oversized McDonalds arch and cocktail stick). But who knows whether or not in 1997, regardless personal feelings on degrees of quality, an album like that would have ever taken off for them.
The big, main, huge difference though is that the birth of Pop at the very least needed the modesty and humility they brought to the birth of ATYCLB. Switch the arrogance of Pop to ATYCLB and it would have failed too. Switch the humility of ATYCLB to Pop and it stood a great chance.
In a sense it's, "Looking for a sound that's gonna drown out the weather" vs "I'm just trying to find a decent melody, a song that I can sing, in my own company."