The usage of Could.
The fire spread through the buildings very quickly, but fortunately everybody was able to/managed to escape.

In the case, why "Could" cannot be used (A grammar book says that it can't be used in the case)?
I'm guessing that If i say that "everybody could escape", it means they could do(escape), but they died.?

Question

The usage of Could.
The fire spread through the buildings very quickly, but fortunately everybody was able to/managed to escape.

In the case, why "Could" cannot be used (A grammar book says that it can't be used in the case)?
I'm guessing that If i say that "everybody could escape", it means they could do(escape), but they died.?

Answer

You are right.

When used to refer to the past, "could" refers solely to an ability. It describes a 'state' rather than an action. If you want to say what somebody actually did, you have to use "was able to" or "managed to". You cannot use "could" in this context.

Answer

It's just that "was able to/managed to" put more emphasis on "ability" than "could" in this particular context. Just shades of meaning.

Answer

If u use could then you mean that the people have been able to escape but unwilling to