I don't think Putin and Trump are afraid of each other, neither are they great friends with each other. But they are both willing to have a dialogue with each other on various issues. Which is a million times better than what the useless trio of Biden, Zelenskky and rest of the world have managed to do among them.
If Trump has a special relationship with Kim Jung Um, he will do the same with Putin. Trump believed, countries who relied heavily on America, for survival , are a bunch of coward and wasted America's trillions of dollars. To save America from losing too much money, and to help tone down aggression, is to make friends and Putin is one of them.