[Praxeologue]

I don't think the gay cardinals "had anything" on Benedict --- if it's blackmail you're implying. I think they just blocked him in all the complicated, underhanded, lying, devious, hostile-oppositional, passive-aggressive ways they can. Maybe they threatened other innocent parties, maybe an array of them, who they could drag through the filth or even physically endanger.

Then why didn't he stand and fight the evil, as a true leader would?

The plausible explanation is that he was complicit and the Lavender Mafia could prove it.

[Mrs. Don-o]

It’s all conjecture at this point. I would think standing up publicly to threats would be a good thing, but I know -zero- facts about this case.

[Bubba Ho-Tep]

Another plausible explanation was that he was an old man who was basically an academic theologian, which is not a particularly useful skillset for running a major institution in a time of crisis. He acted in what he saw as the best interest of the church.

[dmz]

Yours is A plausible explanation, not THE plausible explanation.

Another, IMO, MORE plausible explanation is exactly what Francis suggested, he was old, tired, and lacked the strength to continue in his duties.