Investors like to see a company buying up tangentially related businesses, it's good for business!

Investors like to see a company divest themselves of non-core-competency sections of its portfolio, it's good for business!

Investors are sheep.

If they paid more for it than its worth, than they lost money the instant they bought it. If they sold it to a company that thought it could increase the value of bandcamp by owning it, then they might have gotten more for it than it was worth when they owned it, hence increasing their own value (or at least making a valuation which was previously potential concrete).

I'm not an accountant, but I know enough to have a sense of much "creativity" is possible. The purchase price might be in the past, while costs are ongoing. Yes there would be a markdown from purchase to sale, but that's a different line item from the annual run rate.