Let's analyze.

Fredo had already proven himself disloyal to the Family by taking Moe Green's side in the buyout meeting years earlier. While failing to see the business end of Michael's intentions...he also went straight over Mike's head by asking Tom to speak to their father. Complete ignorance and to top it off, disrespect.

Years earlier than that, Fredo clearly bungled at the attempted killing of Don Vito. While he may not have been able to prevent the actual shooting, his clumsiness with the gun allowed BOTH hitment to flee without even a shot fired at them. In addition to this, he sat and wept over his wounded papa, instead of screaming for assistance. Even if you think a person is DEAD...you do SOMETHING!!!

Remember again it was SONNY, not Michael...who sent Fredo off to Vegas for a rest.

I think Fredo proved several times over the years - to Vito and BOTH his brothers - that he was unfit to be kept 'around the top'.

Apple