Yeah, like where is it written that a new rifle, caliber, bullet, sabot, etc. has to actually be better for us to buy it? Come on, now - if that were true, we'd all have a very small collection of guns, and only one can of powder and one box of bullets, right .
But - I agree with what's been said here - the .52 was probably an attempt to gain more "market share" - and it didn't fly. Look at how this is continually being done in the centerfire world. New calibers are constantly being offered - and of course, to shoot that new caliber, you need a new rifle, new dies for reloading, etc.
Over the years, some "stick" and others don't; that's the name of the game.

IM jaybe