The unsatisfying answer to all of those questions is the same: Because he's Donald Trump.
As he spoke, his campaign (his campaign!) e-mailed a slew of reporters (not BCC'd, mind you) copies of his remarks as prepared for delivery. Over the course of what he actually said, he could have given his prepared remarks 16 times over.
He was supposed to say:
Our country is in serious trouble. We are not respected by anyone. We are a laughingstock all over the world. ISIS, China, Mexico are all beating us. Everybody is beating us. Our enemies are getting stronger and we are getting weaker.
He actually said:
It's great to be at Trump Tower. It's great to be in a wonderful city, New York. And it's an honor to have everybody here. This is beyond anybody's expectations. There's been no crowd like this. And, I can tell, some of the candidates, they went in. They didn't know the air-conditioner didn't work. They sweated like dogs. They didn't know the room was too big, because they didn't have anybody there. How are they going to beat ISIS? I don't think it's gonna happen. Our country is in serious trouble. We don't have victories anymore. We used to have victories, but we don't have them. When was the last time anybody saw us beating, let's say, China in a trade deal? They kill us. I beat China all the time. All the time.
And that's editing out the part where he called immigrants from Mexico rapists. (But "some, I assume, are good people." Some.)
There were 91 prepared words before he announced his candidacy. Instead, he took at least 1,700.
The exercise here is ostensibly to fact-check what Trump said. That's what I've been tasked with: fact-check Trump.
"When did we beat Japan at anything?"
"Last quarter, it was just announced our gross domestic product -- a sign of strength, right? But not for us. It was below zero. Whoever heard of this? It's never below zero."
It's frequently below zero. When it's below zero for two quarters in a row, that's usually used as the marker of a recession. There was a recession recently. (Also, first-quarter GDP data recently has been weird.)
Update: As was pointed out to me on Twitter, what's addressed above is GDP growth, not GDP. The gross domestic product has never been below zero, because it can't be.
"Our labor participation rate was the worst since 1978. . . . And our real unemployment is anywhere from 18 to 20 percent. Don't believe the 5.6. Don't believe it."
The first part is true, but part of that is because of demographic changes -- baby boomers aging out of the labor force. The "real unemployment rate" is a term often used to describe the U-6, which is the unemployed plus part-time workers plus discouraged workers. That "real unemployment rate" is higher, at 10.4 percent.
On Obamacare: "Yesterday, it came out that costs are going for people up 29, 39, 49, and even 55 percent, and deductibles are through the roof. You have to be hit by a tractor, literally, a tractor, to use it, because the deductibles are so high, it's virtually useless. It's virtually useless. It is a disaster."
Recently, insurers filed requests for increases to premiums. Those are negotiated down, as explained here.
But how do you respond to "literally, a tractor." As in, Trump thinks that for you to avoid getting a deductible you must have been hit by a tractor? What does that mean?
This is the whole thing about fact-checking Donald Trump: He is un-fact-checkable. That's his gift and his angle. As he made clear today, he says whatever he wants for as long as he wants, because, why not? If I sat down with him and said that he was wrong on GDP or wrong on premiums, he would call me a hater and a loser and disparage my dog or something. Who knows? Who knows?!
Treating Trump's arguments as serious is like treating Siri's arguments as serious. He's programmed to talk about how he's the best and President Obama is the worst and he can fix everything. "Donald, what time is it?" "I can tell you because I own the biggest, most luxurious watch in the world," etc. etc.
So here's the fact-check: Much of what Trump said is nonsense. But you knew that.
If nothing else, let his candidacy serve as a reminder that no matter how rich or powerful you are, it's useful to have someone around who can say "no."