I think you are being too harsh! on Tom
Sicilian Vito the most experienced, long reigning top Mafia Don “wasn't on the lookout for the irrational need--compulsion--for vengeance†by Sollozzo after Vito's refusal to help with Sollozzo's narcotics trade
As Vito said in the Garden scene Sicilian “Santino was going to have to go through all this†ie: Don in training didn't see it coming either
Then, what chance Tom “non-Italian uninvolved in the muscle end of the business†with his lawyer “background and training†and not a wartime consigliere have, to see it coming
So how “old Genco [this wonder! consigliere with all his heroics!] would have smelled a rat" and “Tom didn'tâ€
I doubt “Michael blamed Tom for Sonny's death†even if “Tom had some culpability in Sonny's death†as unltimately and undoubtedly "Sonny's uncontrollable temper and poor judgment sealed his fate"