My questions are many, but let's start with the big two?
1) In the immediate aftermath of 50 people dead (albeit only 20 were known when he tweeted this out), who wrote to Donald Trump and said, "Congratulations on being right!"? Did they have happy face emoji's with the "good job" tweet?
2) What makes Trump think that he broke some amazing ground by saying we would have another terror incident on American soil? Is he that oblivious to what others have been saying this same thing since (at least) 2001? George W. Bush said this in 2001 (link) and every politician, law enforcement officer, foreign service employee and business has said it since. Mr Trump, you saying this wasn't smart or a break though, it was just common sense. No police force can stop every single attack - particular those carried out by a single assailant (radicalized or mentally unhinged or both). And your "policies" (no Muslims allowed into this country) would not have 'fixed' this.
And, I would normally not say anything like this. But then, in our country tragic events during an election campaign didn't used to be a cause for partisan sniping. But letting a blowhard asshole upend our democratic process during a tragedy is wrong, and pretending he is a "statesman" that cannot be criticized plays into his tiny tiny hands.
He is an asshole for this. Who wakes up, sees 20 - 50 people were killed in a terror / hate attack and says "Wee! I get to be right?"