Over time, I get the impression that Trump's opinions are one-bit binary.
Jeff Sessions was a great guy, then he recused himself, and he's a disappointing, beleaguered guy who he regrets hiring.
NATO is terrible, obsolete, a waste of time. 24 hours later it goes to being wonderful.
I don't think Trump flip-flops as much as he rounds up to 100% and down to 0%. It's a toddler mindset, where there is no gray area. Everything is either the best thing that ever happened, or the worst tragedy imaginable. Where other people might ramp their rhetoric over time, like setting a pot to boiling, Trump is like hitting the pot with a blowtorch. Or dropping it in liquid nitrogen.
I think its why he can't bring himself to criticize Putin on anything, he's still rounding up to 100%. Should Putin do something to provoke his ire, Trump will immediately round down to 0%. Kim Jong Un was at 0%, a maniac, a madman, a sick puppy who deserved assassination. Then he crosses the threshold to round up, and he's talented, smart, and honorable.