I had to give this some thought...
He was not Bruce Dickenson that was the problem. I liked him with Wolfsbane, too bad that band was a casualty. He is a great singer but it's sort of like how would Zeppelin be without Plant but someone who mimicked well? Halford vs Ripper, no contest. Brian Johnson not in AC/DC???? Who would listen? Who would care? The only band that I see a singer stepping in and being successful is Journey, that guy is GOOD (whatever his name is LOL see what I mean?)
The three Maiden albums he did with Maiden did not sell great, the fans spoke and when Dickenson came back, Maiden immediately took off where they left off when he left