You know, like setting up a company, designing other games, having an office space assembled for months for some reason and hiring new employees.
I hate to be this contradictory, but the idea that any of that "kept him too busy to work on Minecraft" is complete and utter bullshit.
The popularity went to his head, and he got lazy.
And yeah, he is incredibly skilled at churning out content under pressure. Keeping with a project doesn't seem like something he has had a lot of experience with.
No, he's not. See every update he's promised ever. He waits until the last minute and does as little of the originally-promised content as he can get away with, throwing the rest under the rug.
He's good at speed-writing, but that doesn't mean he can churn out
content.
(Side-note: Mojang, a new company? Bullshit. It existed nine years ago. Notch was just as lazy then as he is now. He left his spot on Wurm Online because it got into a very similar state as Minecraft is now.)
Sometimes I wonder how people are so blinded as to his nature. He doesn't make any attempts to hide it.