Yes, it was because they all testified to the same behavior on Cosby's part including how he drugged them.Have you been following the legal rulings?
Just curious how the Commonwealth won the "prejudicial vs probative" debate on this one?.... Was it because each witness alleged the odd modus operandi of drugging the vic?
The silly Law School example I remember is: at an embezzlement trial you can't use that the defendant has been thrice convicted of Assault (since it is merely bad acts -- you must have committed the crime since you are a bad person having committed other crimes). However, if a man dressed in a Burger King Costume commits Armed Robbery at six different McDonalds each time coming in with a firearm and saying "I want it my way, give me the money!" That most certainly can be admitted at trial as a pattern of behaviour