EXCLUSIVE

Matt Lauer was able to get away with a lot at the "Today" show for decades ... because the show made its own rules, and routinely ignored its bosses at the network.

Sources connected to both "Today" and NBC tell TMZ, a number of NBC News presidents and other executives tried to set rules for the morning show, but they were routinely ignored.

We're told "Today" operated as a separate entity from NBC management. As one source put it, "They did what they wanted to do."

We're told there were times when an NBC News president would tell the bosses at "Today" they had to run certain stories and the president would be routinely ignored. We're told sometimes the folks at "Today" would ignore basic rules ... such as restrictions on footage it acquired ... despite NBC News guidelines.

One NBC News source said, "'Today' was astonishingly uncooperative with our other shows like 'Nightly [News]' and 'Dateline.'"

As for why this happened ... there are several reasons. Many people on the staff work in the middle of the night, so they rarely interacted with others at NBC. One source said, "It ['Today'] was like a beehive where they only talked to each other." The biggest reason for the culture at "Today" ... as one source put it, "They were in a knife fight every day with 'GMA' and didn't want to hear anyone trying to rein them in."

One reason the attitude at "Today" was tolerated ... the show makes a ton of money for the network.

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Even though Matt would say things with a hot mic -- like telling Meredith Vieira to keep bending down because he likes the view -- such hijinks didn't necessarily make their way to the big bosses because what happened at "Today" usually stayed at "Today."