Aren't there political reasons for skipping Arizona? Even more so than the 6-8 red state shows they are doing in 2017.
They've had other North American tour closers that didn't sell out. Even an arena show in 2001(Britney has venue record 2,000 more people than U2 in Miami).
The Miami, Fort Lauderdale, West Palm Beach metro area had already been played by U2 twice on the Elevation tour before the Miami show. Thats a total of 3 soldout or filled up arena shows in that metro area coming off of a previous low point in the bands career.