Why Italian torpedo boats did well against submarines

Why did Italian torpedo boats perform so well in the Mediterranean, especially against submarines?

Their size made them poor torpedo targets, they were dangerous to engage on the surface, and they were well suited to local waters.

A submarine might be reluctant to spend a torpedo on a small Italian torpedo boat. Surfacing to use its deck gun would expose it to damaging return fire. The boats also operated in Mediterranean waters for which they had been designed. Their size and suitability to the theatre are the principal explanations offered for their effectiveness.