trump will change his story at any given moment - even after making a statement he will immediate contradict himself with the next - just so the narrative of what he's talking about makes himself appear smart, informed, rich, powerful, and winning at everything. As an aside: this is why trump's lawyers are terrified of him taking the stand in Mueller's grand jury investigations: even *if* trump is actually innocent (insert author's eyeroll here), trump's inability to stick to a story would make him seem guilty. trying to cover up for something, and/or mentally unfit (in trump's case, it's honestly all three, but I digress).
In short: trump will ALWAYS lie when it makes himself look better than everybody else.
This is an issue now because of his recent lashing out over criticisms about his administration's failures to respond to Puerto Rico's need for disaster relief after Hurricane Maria.
trump had made statements earlier - during the buildup towards evacuating and securing the Carolina coast for incoming Hurricane Florence - where he bragged about getting "an A+ grade" for his handling of previous hurricane relief efforts (this is including Harvey in Texas and Irma in Florida, both of which haven't been completely recovered).
Apparently there were followups by the media pointing out that the massive death toll in Puerto Rico - more than 2900 lost - doesn't necessarily equal an A+ grade, so trump got on Twitter to blast a conspiracy-addled excuse (via Steve M. at Crooks and Liars):
3000 people did not die in the two hurricanes that hit Puerto Rico. When I left the Island, AFTER the storm had hit, they had anywhere from 6 to 18 deaths. As time went by it did not go up by much. Then, a long time later, they started to report really large numbers, like 3000...
.....This was done by the Democrats in order to make me look as bad as possible when I was successfully raising Billions of Dollars to help rebuild Puerto Rico. If a person died for any reason, like old age, just add them onto the list. Bad politics. I love Puerto Rico!
No one had even suggested before this that the investigation had been faked or staged. trump's excuse came across as similar to the Sandy Hook narrative of "staged event" and "crisis actors".
And now, rather than argue about the size of the tragedy being overwhelming, rather than admit even in part that "things could have been handled better," trump would argue the whole thing is a partisan lie.
It doesn't help one damn bit that the Republican Congress refuses to open hearings into Puerto Rico's situation and the relief efforts. Back in 2005, when Katrina devastated New Orleans and the Gulf Coast, the Republican-led Congress did hold investigations into what went wrong (because God help us we don't want those disasters happening again). This year's model? These Republicans know damn well they have to play along to trump's lies, otherwise their whole house of cards collapses on itself.
Because this is the Second Rule of trump's Lying: trump lies to force his underlings to prove their loyalty to him. They have to accept and defend his lies, at which point he owns them as co-conspirators in those lies. (Rule 2B: Once you become trump's bitch, you will ALWAYS be trump's bitch)
The first thing - LITERALLY the first thing - that happened with trump's administration is that he sent Sean Spicer to exaggerate the inauguration turnout as "the biggest ever" when photographic and video evidence proved it was less than half the turnout for Obama's in 2009. This was for two reasons: 1) trump's Id had to be satiated with the belief he is more beloved than his enemies, 2) trump wanted to test Spicer's loyalty. That Spicer didn't do a good job of it was why trump soured on him and forced him out. It didn't matter that reality refused to conform to trump's will because most of the media and the nation either ignored or mocked him on this grandstanding: All that mattered was trump's bubble remained happily closed.
For all the Republican grousing in the shadows - the disdain the long-standing membership has for him has already been well-documented, it's just NONE OF THEM WILL OWN IT PUBLICLY - that "nothing sticks" to trump, the only reason that shit doesn't stick to trump is because NOBODY who can hold him accountable will. Too many of those grousing Republicans profit from trump's misrule and so they won't do anything to disrupt that.
The sad truth about lies, however, is that no matter the lie it will never fit into the reality of the world around us. trump can say 1000 lies a year and none of it will change the fact that thousands died in Puerto Rico. trump can lie about tariffs, and the economic reality of price increases will eventually force businesses to lose profits and close. trump can lie about immigrants, but it doesn't change the fact that many coming to our shores and borders are doing so to find better lives for themselves and are willing to be law-abiding citizens. trump can lie about the dangers of foreign powers, but invading them isn't going to make the United States stronger or safer (we've learned THAT lesson from the lies that led us into Iraq in 2003).
Lies eventually defeat themselves. You can't lie about the waters flooding your home as the hurricane hits. You can't lie about the failures of high tariffs when too many nations oppose them and starve your own businesses out. You can't lie about separating families at the border and shoving 5-year-olds into baby jails and call yourself honorable. You can't lie about war and walk away with clean hands.
The First Rule of Lying: Sooner or later the bill for that lie comes due.