Why the F7F Tigercat enters the development path

Where does the F7F Tigercat fit into an alternate development line built around the F4F and F6F?

It appears when designers reach the practical power limit of a single engine and use two engines to obtain the performance the mission demands.

The F7F enters this development path when a single available engine can no longer supply the desired performance. A second engine offers a path to more power without waiting for a major engine breakthrough. The answer frames the Tigercat as a response to propulsion constraints rather than simply a larger successor chosen by preference.