Really though, that place seems wayyy too huge for a dude like him. He could've kept that $70 million and probably redid a place in Sweeden that would allowed perpetual heat with an indoor pool in Sweedish winters. But I guess he was tired of his homeland/Sweeden and wanted to live in California where he could do "cold Sweede winters" in the mountains(?) and surf the same day.
Dude's got (IMO) a shitty personality though. "Fuck Occulus for 'selling out' to Facebook!"
"But, Notch, you are selling Mojang and Minecraft to Microsoft!"
"... LOL DON'T CARE. NOT SAME THING. BYE GUYS! *pulls millionare parachute*"
So his girl was basically like "you gotta shitty rich people priorities now meh."

I don't think he was with this girl he's talking about when he bought the place. He bought it RIGHT AFTER the Microsoft sell. IIRC he was still single at that time. But how would I know? I don't follow Minecraft or him because like the above example he's a (IMO) "terrible" person to be around because he has weird mindviews on shit.