I think a lot of what Michael does stems from his intellectualism. He just compares and acts: once Carlo is killed Fredo can't be spared, and if Fredo is killed the others have to go.
I reckon Carlo's murder was a no brainer No way he could be spared
I believe Fredo was going to be spared
Michael was still trying to get Fredo out of Havana saying Fredo was still his brother
Michael told Tom at the Desert Inn, "I know Fredo's scared, tell him
everything is all right. Tell him I know Roth misled him and he didn't know they were planing to kill me"
Then Fredo readily hurt Michael again by deliberately withholding the information, not telling him about Pentangeli's survival, Questadt belongs to Roth because Fredo obviously still wanted to harm Michael again He was still trying to send Michael to Prison
No doubt Fredo's actions were continuously treacherous
Fredo's seemingly untenable situation.....Besides
if Mama had lived longer....
