Right, i'm totally confused and probably about to make a total idiot of myself but here goes.
Hero is all in for less than the blind. So for Rette to think he is ahead with A3 is not ridicolous in my opinion, Hero could be pushing with anything from J2+. He then tries to isolate the all in player by raising (all in was prob too much), again not a bad move as his A3 is prob fav heads up with all in player but not likely to be fav in a multi-way. Mic might think that Rette is trying to isolate the BB by raising with a marginal hand. If i was Mic, I would put Rette on anything from QT+. Mic might think his ace high is best in this situation and so calls. I wouldn't have called, but i can see the logic in it.
Maybe i'm missing something but i really dont see it as being a bad play on either players parts. A bit loose, but not crazy. The A3 raiser was isolating, the A5 player thought he was ahead so called. Also the A5 player didnt care about the hreo. The side pot was 10x what the main pot was so all he really cared about was what Rette was going all in with, for all he cared the hero could have aces as the main pot was isignificant.
Maybe i'm having a

and if my reasoning is flawed, can someone come down and hit me over the head with a hammer. Would be intersted in understanding whats wrong with the above.
Sorry, none of that makes sense (apart from the inital re-raise with A3) when you consider that at the late stage of a tourney for two big stacks to come together in such an obscene fashion with such shitty hands! Regardless if he thinks his A5 is ahead at that time, do you really want to put your whole tournament on the line with that hand? No, you fold, let them go heads up and find another spot.
Just looked at the chip counts again. A5 boy had double A3 guys stack. I take that back... still a bit crazy though.
I agree its totally loose/crazy and not how i would play, but i think ridicluing the guy for getting his chips in the pot with the best hand is a bit harsh.