1. Johnson resigned on March 29, 1994, rather than Jones firing him. Johnson wrote down he was only to be in Dallas 5 years. Allowing him to leave was Jerry's biggest blunder.
After that (in any order):
1. Not getting AP, not drafting Randy Moss, not getting D. Henry
2. The Joey Galloway trade.
3. The Roy Williams trade and new contract.
4. Keeping Jason Garrett as HC for so long.
5. No succession plan for replacing Troy Aikman.
6. The 2020 defensive roster/coaching failure.
7. Not drafting T.J.Watt. Instead, we got a blah Taco.
And there's a bigger theme in all these decisions: The GM Jerry Jones and his unqualified ability to make personnel decisions while also retaining final control over football operations when he has no expertise to do that either.