Not sure how you figure that. Did they win 12 games because of trubisky or because they had the easiest schedule and best defense? Jim Miller/Shane Matthews won 13 games with great defense. As did Grossman. And they did it in John Shoop/Ron Turner offense, not a Matt Nagy offense.
It's a team game - and it's clear Trubisky is a significant part of that. Listen to players talk about him, listen to coaches praise his attitude and aptitude. It's actually why obsessing about individual statistics is a folly , more so whether a magazine or website ranks a player above of below others.
I get it's a major part of watching US sports, and something that clearly doesn't have the same level of importance and engagement in other countries. But at the end of the day, the team with the wins to get to the playoffs, gets to the playoffs and that's what matters, not whether the QB was ranked number 7 in Vogue or Harpers Bazaar.
Trubisky, after a full year with Nagy, clearly has the respect of his peers - and clearly he is a big part of the esprit de corp that seems to be at the hart of the changing of culture at Halas Hall. That to me is priceless, and will reap rewards.