The thing is with the mid-terms almost upon us, you can easily guess the false-flag argument: if these bombs were from pro-Trump crazies it would do obvious damage to floating voters' perceptions of Trump's administration while galvanising them to vote otherwise. Ergo, a pro-Trump crazie couldn't have been the culprit.
My own view is that lots people are very stupid, and the problem with false-flag conspiracy theories is that while historically a few have been proven correct, many of them are difficult to organise...and people are stupid, even those with the power to organise false flags.
I wouldn't completely discount it, but my money is on an idiot or three.