This depends partly on the fact that their business models are largely oriented to credit risk, which especially under Basel II was penalised vis-à-vis market risk in terms of risk weights; and partly on the liberal use of output floors in the Bank of Italy’s supervisory practices, already under Basel II.
The use of output floors, set at adequately high levels, has been recognized as a useful tool to address the variability in the capital requirements for credit risk. See, e.g., Basel Committee on Banking Supervision, Reducing variation in credit risk-weighted assets – constraints on the use of internal model approaches, March 2016.