Let's face it. Vincent was really the only choice left. He was the best out of the barrel.

And it was also a way for Micheal to do the right thing, for once, on behalf of his blood family. He saw that Vincent was passionate in wanting to take over the Family, so Michael used that as an opportunity to protect his daughter from the horrors that she would have been subject to, much like her mother, if she had kept a relationship with Vincent.

Michael finally did what he had to do to protect his blood family, but it wound up being a little too late.