To explain this, you first have to look at this man:
This is Elon Musk, not only a grown man, but the single richest person in the world, jumping around like a three year old at a Trump rally.
Why is the relevant to the question?
Because it’s a perfect demonstration of those that want to acquire more and more, like Trump and Musk, can never have enough. They always crave what anyone else has.
In Musk’s case, he had more money than Trump and was a much better businessman than Trump. But he didn’t have the adulation. Trump had adulation and Musk, the richest man in the world, has no problem demeaning himself just to try and share a little of Trump’s adulation. But it was a waste of time. Trumpers love Trump and only Trump. Elon was never going to be anything other than a side show.
Trump’s attitude to Obama is similar. Obama has respect. People all over the world respected Obama. They may not have necessarily agreed with his policies or his actions, but they respected him as a man and a human being. Trump wants that too, but just like Elon, he has no idea of how to get it. His only response is to shout and scream, stamp his feet and wave his little hands in the air like the misbehaving toddler he is. And just like Elon, the more he tries, the more stupid he looks. It’s really all a bit pathetic.