You think a team can change an entire defensive gameplan based on video tape they took of hundreds of signals during the game?
Having played a ton of football in my life. Yes.
....especially if you already have a nice database of already gathered footage and signals from previous gameplay.
Add that with the "radio frequency issues that occurred during the game." and there is no telling what kind of two way comm these guys had going on that entire half.
Once a simple "sky" or cover 1 signal is picked up from a hand gesture a simple audible sent from whomever to the QB helmet of brady is all you need to dissect those db's.
Don't get me wrong it was a slick idea, but they got greedy,got sloppy and got caught.