I think Trump's praises may increase his chances for Putin to accept Trump's proposals. IIRC Trump wrote a book about making deals that's why I believe it.

Besides that I think that Putin made genuinely smart strategical steps to ensure that nobody will get between him and Ukraine... How it will turn out we yet have to see.

Cornering a leader with nuclear capabilities benefits nobody and can get dangerous, leaving him with nothing to lose. I think Trump wanted to use Russia to counter China.