IMO, Ralph is not dead because of Tracy. With his erratic behavior, he was a liability to Tony's organization and had to go, one way or another. Meanwhile, he made a lot of money for everybody and, as far as Mafia codes go, he did nothing wrong. One had to kill him in such a way that the NJ and NY organizations did not protest, or dispose of him at a time when it would not be clear who was responsible.

In view of this, Tony spent quite some time building a case against Ralph in his own head and waited for the right moment to come. During that time, the murder of Tracy, the problems with Johnny Sack and Paulie as well as Ralph's sexual perversions supported Tony's thoughts. By then, he needed a good excuse to kill him and the arson thing came right on time.