This is a very interesting topic but most scenarios mentioned here contradict each other.
I will try to make a more mature approach based on experience...
I firmly believe, that the truth is that when Bruce left the band it was predetermined from the management that he would take his time off, do his solo stuff and after some years they would do the reunion. Of course no one told Blaze or the fans about this, because this would hurt his motivation and determination. Its simple as that. They wanted Blaze to give his full potential to the band and this wouldn't have worked out if he knew that this is his final tour or his last studio album with Maiden. And the management/record company knew that the announcement of a reunion "out of nowhere" would maximize sales and fans would be ecstatic about it...And yes we (and Blaze Bailey) have been played but that's how music industry works...
I remember talking about this matter with one of my best friends who is also a huge Maiden fan and here is what we came up with:
- In the early 90's Maiden were starting to be considered or were already considered and seen as an 80's band, the kind of band you tend to think more about what they were and what they've done than what they're doing or might do in the future. In other terms, Maiden were no longer one of the most important bands but were now part of the metal landscape, just one among many others
- Two options from this point: continue the same way with the risk to become just what some other bands became, which is no matter how great the albums you relaease might be, no matter how great you are as a live band, it's just that less and less pople care because you're one among a lot of others (thinking of Saxon as a perfect example) and sooner or later you might be totally forgotten and become just a nostalgia act
- Option two: totally change this routine with an "unforeseen event" (Bruce leaving) and now that this even has attracted the attention of all the metal community, bring in the band a singer that you know he's not only very different from Bruce but also won't be able to sing the songs on the same level
- OF course, the speech you'll be giving in the media is that this new singer is amazing, you couldn't be more happier and so on...but at the same time you don't help him at all per example when it comes to adapt the songs to his vocal range or properly prepare your first tour with the new guy (an interesting read is on the Maiden Revelations website about this with all the story of the Blaze era)
- So what happens with this: the legendary singer from a - once - legendary band is replaced with an "average" singer that isn't able to sing these classic songs properly and also in terms of stage presence/interaction with the audience, it just can't be compared. Everyone starts remembering with a certain nostalgia of these days with Bruce and how it was great compared to what the band has become
- And when the band hit rock bottom, when all the metal community is now "making fun" of what was once a great band, with a great singer then comes the news: the legendary singer is back and he doesn't come alone, with him comes also the guitarist of that golden days
- Results: these news are all over the metal media, Maiden becomes again one hot name in the metal scene and everyone is now looking forward to see them live with the one that is their "true and only" singer and as a bonus, we get to have their 2nd guitarist of the legenday 80's period. Now with a good album and with a lot of touring, here is Maiden back from the dead!
Ok, as a conclusion this is a story for which I don't have a single proof and it can be seen almost as a conspiracy theory but on the other hand, when you have a manager as clever as Rod Smallwood that knew what decisions should be taken in order to keep Maiden at the top, let's say I wouldn't be surprised if this was the truth or at least part of it...but in the meantime, for lack of proof, its just a theory made by two fans that sometimes would like to see beyond the well prepared speech that is given to us.