Ryan Pace does not have long term security to overpay
The other factor is the extension. If Pace knows he needs Robinson to win in 2021, why not pay the man and keep him around even longer? There could even be the benefit of lowering his first-year cap hit due to his signing bonus.
The issue with that is that while Pace has a win-now mandate in 2021, that means he is not guaranteed anything in 2022 or beyond. Ownership has to walk lightly with how much future draft capital and future salary cap assets can be spent.
Paying Robinson can reduce his first-year value, but it leaves bigger cap hits for a potential new GM. Robinson could be worth that, but tying up future space makes a new job less attractive. It is a difficult line to walk.
However, it does leave not only Ryan Pace but the ownership group in agreement on how they view Robinson. They need him for 2021 and cannot get better than him, but they also do not want to lock him up long term. For the Bears and Pace, the best idea is to force Robinson to play on the tag.