This isn't surprising, Cartmell has been running a pretty lacklustre campaign. Walters is the more competent Cartmell fighting for the same voters, and then you've got Caterina and Jaffer cannibalizing another anti-progressive portion of the vote.
Knack is the only progressive option with name recognition, and idk he doesn't have 4 other candidates cannibalizing his vote share. The Sohi/Iveson coalition needs to just show up and vote behind one candidate making it an easier path to the mayorship. That's not the case for anybody else, and it's one of the biggest issues when you have a crowded field, but crowded only for conservatives and centre-right folks.
If I was Cartmell, I'd be pissed that Walters put his name into the ring, along with Jaffer. Caterina was always going to run anyway.