interview with trump, page-5

Instead, he oftentimes acts like a clown with quasi-dancing and his other antics?

That's how he sprinkles his enchantment pixie dust, giving a blind love infatuated mancrush to all the gullible.

Why doesn't Trump talk like this (like in that interview) and appear serious when he gives speeches to his supporters ??

Makes them believe everyone is corrupt that calls him to account when it is obvious to all those that are not under his ridiculous spell that he is very corrupt.
He believes he is above the law.
He's fooled so many with his Taliban surrender, support for tyrants, terrorists, people and drug smugglers.