Marvel, DC, Image and the rest are operating from the same doomed and increasingly obsolete business model that's doing so poorly for traditional newspapers. Marvel's had financial woes for years, recently turning around in the wake of a very successful movie house. It doesn't surprise me that they've decided to cash out, nor does it surprise me that an unstoppable media powerhouse like Disney would buy them. It dovetails very nicely into their existing operations, and Marvel - unlike DC - has a wealth of future potential movie offerings.
And I'll betcha this: Under Disney's watch, we won't see craptacular offerings like Wolverine Origins.