I always thought it kind of odd how quick tony folded on assisting and basically handling this entire hit. Kind of shows that in the end he pretty much had to go along with new York.

I think one reason that Tony initially refused the request was because it came through Phil. Even though Johnny Sack was imprisoned and Phil was communicating his request I don't think Tony liked Phil and wasn't going to go along with orders/requests from a #2. When Johnny asks at the wedding Tony hesitates but it is a "boss to boss" favor. I also believe that Tony sees what his future could be if he ever winds up incarcerated and he wants to put some goodwill in the bank.

Tony folded, cause he knew what Johnny Sac was capable of even behind bars, since he still had loyalists in his family. Tony refused the request from Phil cause he didn't like him and knew Phil was going behind Johns back, remember at Bada-Bing during the meet when Phil said it would be best if John didn't know about the deal they just made. Also maybe in the back of Tony's mind he held Rusty responsible for allowing Angelo to reach out and use his cousin during Carmine and Sac's war during the fifth season.

Saw an interview with Frankie Valli regarding Sopranos. He said he auditioned for a different part 4 years before he got the role of Rusty. He didn't get the part but David Chase contacted him several years later and created the Rusty character specifically for Valli. Frankie said sure he will play the part of a capo from Jersey... he had a little experience with that stuff.

Tony knew it was in his best interest to stop refusing the NY bosses.