I'm sure anyone selling to Google is looking for both a big payday and the opportunity to do things with their products/services they wouldn't have the resources to do otherwise. The exit strategy for owners at a lot of small technology companies is acquisition by a larger company.

I'm not sure Google is breaking any laws by purchasing companies and then not doing anything with them. It may not be sensible and it may not be ethical (depending on expectations), but I doubt it's illegal.