Aston Martin
***After Ford dropped Aston Martin, it became enormously profitable again.***
You are correct. However, the key phrase here is "after Ford dropped Aston Martin." Chipotle is hugely succesful, yet MCD spun it off. Ford's turnaround CEO from Boeing, and he realized less was more.
Juggling multiple brands may increase sales, but increased profits are the only thing that matter. It's usually a recurring theme on wallstreet: Buy brands to increase sales, then hire a turnaround CEO to come clean up the mess, who then sells of the brands to get back to its core mission after the company lost its way.
And this rerun has been going on for several decades now.