all the first stories in the newspapers talked about the video AND audio equipment seized that day from the pats sideline.
Nobody ever talks about the audio. That was the REAL scam. They captured signals coming in to the QB and the defensive captain, and Ernie, with his photographic memory, knew the entire playcalling verbiage of every team in the NFL. He heard the signal coming in, translated it to "Cheat" language and funnelled it back to Tommy and the defensive captain.
They received it as "watch for this". Those calls from Ernie gave the cheats an advantage, not a clear cut, "We're gonna kick the **** out of you now." advantage but enough of one to make a few extra plays. Since offense is inherently advantaged over defense, we saw MORE effectiveness from Tommy because he knew the coverage, the called blitzes etc. That made it MUCH easier for him to audible to a run away from a blitz or to identify a WR who could/would be open against the coverage.
Just small advantages that cumulatively added up.
In time, the league began to get wise. The Giants won their SBs because they changed their entire play-calling language before the SB and the cheats had to play an actual game against them. So, in order to maintain an edge, the Cheats came up with myriads of other ways to gain advantages. Deflated footballs, for example.
Folks say that Brady's success in Tampa nullifies the cheating allegations. I would argue that A) the Bucs put together one of the most talent-loaded teams in history to support Brady and B) I still remember ole Tommy getting some pretty ******* amazing calls that first year when the Bucs were starting to look like they weren't going to make the playoffs. You remember that run they went on, fueled initially by a few pretty great ******* calls they got?
I would suggest the league itself (IE Goodell) has a VERY vested interest in Tom Brady looking JUST as successful (or nearly so) with the Bucs as he was with the cheats for PRECISELY the effect of making it seem as though the cheating was either nonexistent in NE or much less pervasive than everyone believed.