Q:

Doesn't multiple inheritance solve all problems that entity systems do?

The question is pretty self explaining: doesn't multiple inheritance solve all the problems that entity systems also solve?
I just remembered a term called "multiple inheritance", and that seems to solve a lot of bloating problems that classical inheritance imposed.

A:

No, multiple inheritance does not solve all the same problems that entity systems do: entity systems and multiple inheritance are two very different things. You can build an entity system with or without multiple inheritance and similarly you can utilize multiple inheritance without building an entity system.
Traditionally, component-focused entity systems are developed because of a desire to move away from heavy inheritance in any form, aiming instead for composition. There is sufficient literature and discussion elsewhere on this adage, for example on programmers SE or SO itself, and it the larger question of why to prefer composition is sort of off-topic for game development. In short, however, it's an approach that tends to lend itself to improved mutability and maintainability. 

