We can't let Miami get him. If they get him, we're screwed for a while. We won't be able to catch Buffalo and Miami for several seasons...no matter how good Zach Wilson might be.
Watson jumpstarts a broken down franchise.
If Zach Wilson is a star, we might be in better long-term shape not trading for Watson than we are trading for Watson. We have the draft picks and cap space to build a very solid foundation for a roster, while the Dolphins and Bills will be paying their quarterbacks a ton of money. Obviously, having both those guys in the division for the foreseeable future would be a disaster, but if Zach Wilson turns into a star in his own right, then we could be just as formidable. Not to mention, both Watson and Allen have had injuries in the past, and both play a style where they could get injured again.
Of course, the risk is that Zach Wilson does not become a star, and that risk is exactly why I would pull the trigger for Watson in a heartbeat. If you told me right now that Zach Wilson is guaranteed to become a top-10 quarterback in the NFL, they might be better off long-term not making the trade. But you can never know that.