You do not "know it". You just have conditioned yourself into believe that if Dak can't do it then nobody else can.
I don't agree that their "effectiveness" would have been diminished in Dallas at all. All we've seen is Romo, Dak, and other QBs here for the past quarter of a century fail over and over and it's skewed your view of QB play.
Do I think Mahomes could have won with Garrett? Absolutely. What had Reid won before Mahomes? Alex Smith had Hill, Kelce, and Reid also. How'd he do? What did he lead the Chiefs to? Mahomes was THAT guy INSTANLTY and has lead the Chiefs to at least the Conference Championship game every year he's started.
You continually fall into the trap of overrated Dak and Romo. There are levels to QB play. Romo and Dak are not at the top of the heap where you can say with 100% certainty that if they can't do it then nobody can.
You think everything is perfect in these other organizations? They have no issues at all? What did Reid win before Mahomes? What did McCarthy win before Rodgers? What did Belichick win before Brady?
Why when it comes to these truly elite talents you want to diminish just how much they, themselves, changed the organization they were a part of because they are great? Does it somehow make you feel better ignoring their contributions because in your mind if you put that aside you can continue to convince yourself that Dak is just being held back?
your personality and mindset screams out in these comments and responses. as I said it and you have clearly shown, to you everything has to be black and white because you are unable to comprehend, understand or live in a gray area. thus given I have not shown to be 100% in agreement with you, in your desparation you are trying to paint me as being on the opposite side and 100% on Dak's side. it makes for very interesting psychology.
I am not skewed in my thought about players coming here and losing effectiveness. you are 100% wrong to think that Garrett, Jones and the dysfunctional Cowboys organization would not impact them. I understand that you are obsessed and Dak lives in your brain 24x7, but we have observed other players who come to dallas and become ineffective. its not just a single thing or another, again a black and white view of the world to you, but many different things that when put together impacts the culture, the organization and the team. Mahomes is supported by a great coach, perhaps a future HOF coach. would Mahomes have reached a CFG with Garrett at the helm? you think yes. you questioned Reid and equate him to Garrett perhaps, a coach who did reach a superbowl and other CFGs with McNabb at the helm. so it was not unprecedented for him to have put together a team and find success. Garrett never sniffed a CFG much less superbowl. he never had post season success. he actually managed to choke big games away to give him a chance to get to post season.
now in regards to your Alex smith comment, I am assuming you are saying it takes talent to win and Dak is not talented. I never argued you don't need talent to win. however, talent alone doesn't equal winning which is your black and white view of the world. otherwise Stafford would minimally reach a CFG game or have multiple playoff wins. he is talented. no denying that.
and no I don't think everything is perfect in any organization anywhere in any business. but some are more dysfunctional than others. I have seen that first hand. those dysfunctional teams that lack the right focus tend to not do as well regardless of talent, unless you want to point to dallas being the highest valued franchise and not dysfunctional, which is where the focus of Cowboys is, not winning at any cost which is the results we have seen so far. in dallas brand matters more than winning.
so I think almost all would agree with me that Romo in another organization would have fared better and the rodger's brady's and mahomes of the world effectiveness would diminish in Dallas. would it diminish to a point where they could not win a superbowl. perhaps they could have overcome the dysfunction. what we know is that Brady was a FA and chose to go to Tampa. Jerry Jones reputation precedes him.
you are really struggling. not sure how I can help you