Not at all. I don't believe Bonanno was involved in Maranzano's death at all, although he obviously gained alot in the aftermath. Bonanno did become distant to Maranzano after he became "Boss of Bosses", simply because Maranzano had to deal with everyone not just the Castellamarese anymore.

Bonanno was brought in afterwards for a couple reasons in my opinion.
1.) He was young enough to be cooperative with Lucky Luciano
2.) He had the famalial lineage that gave him prominence over others.
3.) He had actually fought in the war
4.) All of the above, allowed him to keep a lid on the Castellamarese guys, so eveyone could get back to business.