Back in the ancient times that historians refer to as the 90s. There was a console called the Super Nintendo, or the Snes. And on the Snes there was this cool hip game series everyone (and I mean everyone) was into called Donkey Kong Country. The kids said it was "De Shiznit." That was THE GAME for a lot of people. Sure Mario and Zelda existed, but let's be honest with ourselves, Donkey Kong Country > Super Mario World. Also Link to the Past was for nerds.
I really do mean it when I say everyone played Donkey Kong Country 1-3. Hardcore gamers, Casuals, housewives who get bored when their family was busy at school or work. Everyone remembered the game and everyone who remembers a good game remembers a good set of Villians. And boy were the Kremlings memorable. And continued to have popularity in the Nintendo 64 days with the decent but not Banjo and Kazooie good Donkey Kong 64. Things were going so swell... Until the Xbox Nation attacked.
In the early millemia, (2000s) the next generation of consoles started and Microsoft wanted in, so they designed a new console to compete with Sony and Nintendo called the Xbox. The console was a powerhouse with one exception, they had only one game on it that you couldn't play anywhere else! (Until it got ported to PC where everyone could play it.). So one dark cold evening, Bill Gates and his crew of keyboard Ninjas broke into Nintendo headquarters and kidnapped the Donkey Kong Country developer's dignity, and forced it to make what we called Kinect Crap.
Since the company behind the games that stars DK and the Kremlings was gone, Nintendo never used the Villians again to "try bringing something new and original to the table". Unfortionately that made K. Rool and his minions a relic of the times.
Fun Fact. Lots of people wanted Ganondorf to be scrapped from the game and replaced by Ghirahim. We all call those kids losers who don't play good games. The real culprit to blame for that was Nintendo. Because Ganondorf hasn't tormented hyrule since the mid 2000s, since Nintendo wanted to try some "new fresh Villians" for the Zelda series.
King K. Rool is also #1 in all of the Reddit, Smashboards, Gamefaqs, IGN, and most youtuber "who did you vote for in the smash ballot" polls. Followed by Banjo and Kazooie, Shovel Knight, Inkling, Shantae, and the character I voted for, Isaac.
Edit: K. Rool also is a heavyweight Villian who uses an arsenal of dirty tricks to fight. He has been a Pirate, a King, a Boxer, a Blackbelt, and a Mad Scientist (despite being stupid.). He is also known for one of the first real video game fake outs. In the first game Donkey Kong country you KO him and the Credits start to roll... When you think you won and put your controller down, he gets back up and starts fighting way more aggressively than before destroying the credits and causing you to fight him one last time. Then DK steps on his face so hard it fucks up his eye for ever and ever.