Headcanon: Bowser fucking hates King K Rool’s guts, and that’s why K. Rool doesn’t show up more often in the Mario Kart/Sports/Party games.
Like, because, while Bowser is an imperialistic dictator, we know from stuff like the RPGs that he actually cares a lot about his troops/subjects, and there’s a huge degree of respect between them.
King K. Rool, on the other hand, is shown to treat his subjects/troops like shit, to the point where his chief mechanic defected in DK64 and one of his goons takes bribes to let you in to the bonus areas in DKC2, his mad quest for vengance for the Kongs ended up with him inadvertently fucking sinking his people’s homeland, and at one point his troops fucking lead a coup to replace him with a robot after said sinking.
Granted, he was the puppetmaster of that robot, but they didn’t know that at the time!
And, getting into wild speculation territory, I’d bet dollars to doughnuts too that the reason Krocodile Isle was such an ecological trainwreck before it sunk was due to his policies, considering what the factories he installed as a breachead on DK Isle would look like.
Plus, there’s the fact that his basic tactic of “steal his enemy’s staple food supply so they starve to death” is a foul tactic that I’m pretty sure could be counted as a war crime of the level Bowser has never resorted to; even when he was trying to become God in Mario Galaxy.
So, seeing all of this, it’s easy to understand why Bowser would be fucking disgusted with the guy, and would probably be able to convince even the notoriously-lenient Mario (Who has even let the guy who tried to keep him as a permanent painting join from time-to-time) to not let him come after that one time.
Ironically, I think that K Rool would probably greatly admire Bowser, given the strength and greater efficiency of Bowser’s army, as well as how Bowser tends to bounce back from defeat much better than K. Rool’s army…
I HAVE COMPLEX FEELINGS ABOUT THE MARIO SETTING OKAY! JUST BECAUSE THERE IS ONLY THE LOOSEST OF CONTINUITY DOESN’T MEAN THERE ISN’T WORLDBUILDING POTENTIAL DAMMIT!