Again, I don't think it can be stressed enough...
It's not just that the Bears drafted Mitch Trubisky... They gave up 2 3rd round picks, a 4th round pick, and probably $2-3MM to move up to pick Trubisky instead of just staying pat and picking him with the 3rd pick, and if he was gone at that point they would have had Mahomes or Watson available and probably could have traded down to get them.
The Bears gave up a 4th round draft pick and are paying Nick Foles $24MM for three years. They could have not given up that draft pick and paid Teddy Bridgewater just $3MM more a year, or they could have not given up that draft pick and paid either Andy Dalton or Cam Newton essentially nothing. Or they could have waited Jacksonville out and probably picked up Foles' contract without having to give up the draft pick. Or maybe someone else gives Jax what they want for Foles. And then, Oh no! you don't have Nick Foles and maybe you spend that money on a lineman or something.
And not one single bit of this is 20/20 hindsight. The general reaction around the league when the Bears gave Mike Glennon $18MM was, "Who?" They could have re-signed Brian Hoyer for 1/5th that amount, gotten Nick Foles for $1.6MM, Josh McCown for 1/3, Ryan Fitzpatrick for 1/6 or Case Keenum for 1/9.