Why Did Mojang Sell Minecraft?

I got this from the official website:

"Minecraft has grown from a simple game to a project of monumental significance. Though we're massively proud of what Minecraft has become, it was never Notch's intention for it to get this big.

As you might already know, Notch is the creator of Minecraft and the majority shareholder at Mojang. He's decided that he doesn't want the responsibility of owning a company of such global significance. Over the past few years he's made attempts to work on smaller projects, but the pressure of owning Minecraft became too much for him to handle. The only option was to sell Mojang. He'll continue to do cool stuff though. Don't worry about that.

There are only a handful of potential buyers with the resources to grow Minecraft on a scale that it deserves. We've worked closely with Microsoft since 2012, and have been impressed by their continued dedication to our game and its development. We're confident that Minecraft will continue to grow in an awesome way.

Minecraft means many different things to millions of people across the world, and to each and every Mojangsta. We feel that this is the best way for everyone - you guys included - to benefit."

Hopefully that answers your question!