Why is optimistic locking faster than pessimistic locking?
You misunderstand optimistic locking.

Optimistic locking does not cause transactions to wait for each other.

Optimistic locking possibly causes a transaction to fail, but it does so without any "lock" ever having been taken.  And if a transaction fails because of optimistic locking, the user is required to start all over again.  The word "optimistic" derives from exactly the expectation that the condition that causes transactions to fail for this very reason, will occur only very exceptionally.  "Optimistic" locking is the approach that says "I will not be taking actual locks because I hope they won't be needed anyway.  If it turns out I was wrong about that, I will accept the inevitable failure.".