Its because they fired or otherwise pushed out every single original developer towards the tail end of KSP1.
To be fair, KSP 1 was pretty bad on the technical side. And they were laymen, creating what they wanted to create.
They were non-game developers doing a videogame. But they were pretty good programmers for what they put out. It’s still the best and most popular space exploration sim game ever made. The thing does the thing they said it was going to do, it will probably melt your computer during edge cases, but everywhere else it’s a solid game. They even managed to confine the kraken to very extreme circumstances. If it is a hack job but it works, then it isn’t a hack job.