IMO, Johnny Burns didn't have the capabilities to run the family as boss, nor did he have a forceful enough personality to command the family troops. (his brother Sally Burns had even less).

Johnny Morale was largely just a proxy and puppet of Joe Bonanno, who installed Morale as "underboss/acting boss" in his stead because he was malleable and easily controlled. (a smart move actually). Bonanno felt "safe" with Morale.

Thats why as soon as Bonanno was ousted, Morale was pushed to the side and essentially shelved and forgotten about. He didn't have enough influence on his own. He just faded from the scene and resigned himself to an early retirement.

He was no Evola, Galante, or even Rastelli.