Yes I agree that Claudius' character as Emperor doesn't really make sense when you think about it. My alternative theory is that Claudius, who Suetonius does say was known to drink a lot, was so horrified to get the Empire dropped on his head he was basically plastered through the whole of Messalina's reign. By the time he sobered up, he realised it was too late to do any good and that except for the bit about disloyalty to him, the women and freedmen were actually doing quite a decent job running the Empire so he should let them get on with it.