Did you mean Armchair GM’s disagree with other GM’s all the time?
1 GM and HC wanted Geno Smith with a $75M/2 year contract and were prepared to give up a 3rd round pick. Another GM and HC didn't really want Geno Smith at $27.5M/1 year deal and were willing to take a 3rd round pick for him.
1 GM didn't really want to keep Metcalf at $18M. Another GM was willing to give up a 3rd round pick and pay Metcalf $30M per year.
1 GM and HC didn't want to keep Kupp at $15M. Another GM and HC were prepared to pay him $17.5M.
There are always disagreements about pick values, player values, trade values, Draft values, team priorities, salaries, how long a player has left, etc. No-one gets every decision right, and luck plays a part.