Now DT, you know very well that one responsibility of a consigliere is to anticipate threats to the family. Tom did not due that regarding the attack on Vito or Sonny's murder. Thus, Michael's resentment.
How was Tom supposed to stop Sonny? By the time he got outside, Sonny was already gnning the car as Tom yelled at him to stop. All he could do was send the bodyguards who got there too late.
As for Vito, I guess you could argue that Tom underesitmated Sollozzo in that he didn't see Sol was backed up by Barzini and not Tatt. But Vito missed that too. No one saw this coming, and I don't think Genco would have eithr.
