Fair enough!

“no way Tom could have left the Family” when Michael was alive
If Tom had told Michael, "Yeah, I'm taking that offer from the House and Hotels," Michael would have let Tom go....in a box!

However with Michael dead and knowing Fredo was involved....

Tom “both to stay connected with the only family he ever had, and to avoid severing his ties”
Tom does have his own family, wife Teresa, children and might just might couldn't wait to sever his ties, “without Michael, he might have gotten out while he still could”

I acknowledge, Rocco and Neri would need Tom to front the business but still doomed due to the internal war and bloodshed

“Tom knew too much--business/political contacts, and incriminating info on Michael, Rocco and Neri”
Tom “I never know no Godfather I don't know nothing about that. I got my own family” and would / could always plead the fifth Amendment?