This
You have to think of it as a protective move on Apples part (I think I posted this before).
Apple has been the only real game in town, and has a cult following when it comes to online music purchases because of the built in integration to their products. It isn't in any way shape or form the best service to use...in fact it is probably one of the worst, but they are the most convenient for the purchasers of Apple products which has been a majority (though falling off a bit now) for years.
Here comes Dre and company with a brand that is recognizable and has a built in following, he proved that with Beats headphones...in fact he could have packaged bacon wrapped turds and probably moved a couple million units. This is a viable threat to Apples dominance directly because they know that if this goes live Apple now has to offer competitive contracts with artists in order to get their music. This is not something Apple is willing to do because it would be millions a year in profits lost.
So in the long run it is far cheaper for them to purchase and cannibalize as much as they can, including conversion of contracts and technology followed by discarding the rest including but not limited to the dissolving of the Beats name altogether.
Apple stock jumps, products now come with a higher cool factor headset and Dre retires a happy and rich man...everyone is satisfied while Dre and company only had to show proof of concept to get there.