Why do you believe Kevin is really pissed off at Palumbo? Because he says he is? Do people in wrestling really hate each other? It's mostly just theatre.
Almost all of this stuff is just social media exploitation. Mentioning people's names and cashing in. Palumbo makes a video about Kevin and monetises it, Kevin then gets to make a response video and monetise it. It's just a circus of money and if there's no news and nothing but harmony, there is no money in the videos. Do you really think Kevin gets pissed off at people doubting him? Pfft, the dude would be pissed all of the time. He even admitted he had his doubts (though he never admitted that until after the fact).
You read too much into this "beef" shit online. Every one of these people understand that slinging a bit of mud makes money. There might be the odd situation where they don't like it -but believe me, they make more money from a beef video than most other things.
As for all the people you've mentioned - they ALL were making their money whilst in their prime and NONE of them have had to build their following post retirement. That's the difference. Without question, Kevin would easily have been the poorest of all of them when he started his "comeback". Different situation. Kevin needed to do something different and he still does because there is no way he could live comfortably off the money he made this year - he needs to milk it for longer. If he had 1.8million followers on instagram like Jay, he might be able to coast more but at 499k, he has a long way to go.
I reiterate - what Kevin is doing is the exploiting the situation. Whether he is crazy is really moot - what he is doing now is smart and necessary. In a year or two, he can slow down and milk it more like Jay.