In hindsight.. I think the umpires just put the whistle away, and it was Collingwood making all the errors in the 4th with the HTB and high tackles on Tippa, etc. It is perceived as the umpires favoring Collingwood, but it's just that Essendon were playing cleaner at that point and making less of these types of mistakes. Essendon's mistakes revolved more around turn overs and poor ball use - no umpiring influence. Where as Collingwood's mistakes were HTB and high tackling, and I feel like either the umpires were told to let them play on more and not call free kicks... or the umpires were caught up in the game and didn't want to slow it down with free kicks. Notice there was only 1 or 2 50 metre penalties for the entire game? And for a physical game like this where there were A LOT of contests and a lot of contested ball situations, 14 - 17 free kicks is quite a low number.
So to sum up... maybe the umpires were advised by someone high up to ease up on free kicks and 50's in this game, and they got TOO relaxed on it, and these instances we saw with Crisp, Moore, Stephenson HTB were overlooked as they weren't blatant enough, when usually they would be frees.