My take, for what it is worth!
I don't think “Michael actually
wanted to be the Donâ€
Besides it was a given that Sonny was the heir apparent and “legitimization of the Corleone name†under Sonny was not in play?
Michael may have “wanted certain things out of life (power, success, the ability to make his own choices...)†which Michael was going to “accomplishâ€
away from the Corleones crime business - Senator Corleone, Governor Corleone...
I don't believe the below had any bearing to Michael
wanting to be the Don
1. “I'm with you now†at Vito's hospital bedside
2. lighting Enzo's cigarette
3. killing Sollozzo and McCluskey
Michael's involvement was solely and all about protecting Vito, at that stage
Dob_Peppino – Extracts:
Circumstances made it a nessacity He needed to protect his blood family from harm, that was his duty
I believe Michael had no aspiration of “becoming Don†which was thrust upon him
“circumstances: Vito's incapacitation, Fredo's incompetence, Sonny's assassination, making him the default Don†and Michael had to resign himself to his 'destiny'