Regarding Somewhere Back In Time, i have a feeling that things happened this way : with a highly successful album and tour, with the birthday gigs for Number Of The Beast, and with various rants about "having pyramids, robots, and singing about albatrosses next year", Maiden got a bit more attention in the general media and general music circuits. When they announced LAD stage props, their own Boeing 757, and all the fancy stuff, that attention just got bigger.
Prior to the India show, we didn't know the setlist. We only knew hints, but what was certain, didn't affect the setlist type...is it going to be real '80s gems or just the greatest hits? Songs that we didn't know made a difference. People thought that it's going to be '84-'88 setlist, but still they raided ticket shows.
For instance, their last time in Croatia (before this tour) was on Give Me Ed tour. GMETID tour was a greatest hits tour from the whole catalogue, yet they played on a simple football pitch in a small town near Zagreb. It even goes better, they were scheduled in Zagreb's indoor arena, which can house < 10.000 in concert. This time in Split, they played on the biggest football stadium in the country. Again, the stadium (like all other tour venues) was scheduled way, way before anyone knew what exactly are they going to play.
Suma sumarum, Maiden did consolidate and they did play songs which they enjoy and like, eg. Moonchild, Clairvoyant...that was good. However, Revelations, The Trooper, Run To The Hills, Number Of The Beast and Fear Of The Dark don't belong in the original description. IMHO they saw how much people they attracted all over the globe, and they decided to play well known songs outside the era of original premise, to satisfy the "general audience".
If those 5 songs were 5 extra songs from Somewhere In Time and Seventh Son Of The Seventh Son, the tour would have been what it was supposed to be. Those 5 were the variable (x). We knew they're going with 4 LAD songs from Powerslave, 2 elementary (IM and HBTN), and at least 5 basic, well known songs from SiT and SSOASS.
So that (x) was the choice between hardcore fans and general public. When they saw the response to the tour, they decided to go for general public. Which sucks, because history tours weren't concieved for general public, they were there for Maiden fans.