What company buys another company and replaces their existing management with the management from the acquired company?

Quite often, actually. McDonnell Douglas and Boeing, allegedly. Netscape and Collabra:

Zawinski: So basically [Netscape] acquired this company, Collabra, and hired this whole management structure above me and Terry. Collabra has a product that they had shipped that was similar to what we had done in a lot of ways except it was Windows-only and it had utterly failed in the marketplace.

Then they won the start-up lottery and they got acquired by Netscape. And, basically, Netscape turned over the reins of the company to this company. So rather than just taking over the mail reader they ended up taking over the entire client division. Terry and I had been working on Netscape 2.1 when the Collabra acquisition happened and then the rewrite started. Then clearly their Netscape 3.0 was going to be extremely late and our 2.1 turned into 3.0 because it was time to ship something and we needed it to be a major version.

So the 3.0 that they had begun working on became 4.0 which, as you know, is one of the biggest software disasters there has ever been. It basically killed the company. It took a long time to die, but that was it: the rewrite helmed by this company we’d acquired, who’d never accomplished much of anything, who disregarded all of our work and all of our success, went straight into second-system syndrome and brought us down.

They thought just by virtue of being here, they were bound for glory doing it their way. But when they were doing it their way, at their company, they failed. So when the people who had been successful said to them, "Look, really, don’t use C++; don’t use threads," they said, "What are you talking about? You don’t know anything."

Well, it was decisions like not using C++ and not using threads that made us ship the product on time. The other big thing was we always shipped all platforms simultaneously; that was another thing they thought was just stupid. "Oh, 90 percent of people are using Windows, so we’ll focus on the Windows side of things and then we’ll port it later." Which is what many other failed companies have done. If you’re trying to ship a cross-platform product, history really shows that’s how you don’t do it. If you want it to really be cross-platform, you have to do them simultaneously. The porting thing results in a crappy product on the second platform.