Remember that Returns interview people point out to?
The one where they dismissed the Kremlings as if they're essential or not to a DKC game?
I think the way that came out sounding so dismissive to people was what fueled a lot of people's enthusiasm for K. Rool
I'm not saying he wouldn't have been clamored for had that interview not had happened but people positioned K. Rool and the Kremlings as an underdog of sorts ever since that interview (which was bolstered when he wasn't playable in Smash 4 despite being one of the most popular requests since the Brawl era).
Sure it got annoying when people used to reinforce disproven rumors that Nintendo and Miyamoto were resentful towards Rare but frankly it made his return in the series proper all the more worthwhile.
But as for K. Rool himself, he's a fun, memorable mascot platformer villain.
Making the hero stand out is one thing, making their villain memorable is another.
It's inherently a harder thing to do.