Exactly Navaleye.
It was correctly estimated that we would lose ships. Some estimated that we would lose more.
We did.
It is called war.
It is something that military forces have to accept if they put themselves in harms way.
A military force that is unwilling to accept losses is a chocolate fire guard.
Incidentally, since the RN practically invented the airborne destruction of a fleet at Taranto, I think it is moronic to suggest we underestimate the threat.