"Channel" is unwanted because it apparently signifies old media. The Internet doesn't want channels. The reason that "the" is gone isn't explained, but the humble article has a history of being added and deleted on occasion for various purposes.
Back in 1993, the Arnold Schwarzenegger movie "The Last Action Hero" became "Last Action Hero" shortly before its release. The thinking in Hollywood was that "the" wasn't good for marketing the movie. "Last Action Hero" failed to meet box office expectations, however. Perhaps "Titanic" lacked "the" for the same reason; that title served not only as a label for the ship but also as an adjective for the massive production.
If "the" is not good for the movies, perhaps it beneficial in academia. Ohio State University seems to think so because it prefers to be known as The Ohio State University. This is most evident to the rest of America when an NFL lineup is introduced at the start of a game on television. As each player states his name and his college, the former Buckeyes almost always stress this point: "John Doe. Theee Ohio State University." It does ensure that no one is confused by those other Ohio States.
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What all of this back and forth about "the" means for The History Channel is unclear. As the Clash once said, the future is unwritten. Or was that Clash?
A TV channel called "The History" would be pretty strange, don't you think?
Also, it should be noted that The The is perfectly easy to find on Google...they're in the first screenlength of searches with or without quotes.
As for Last Action Hero, maybe that was just the studio being nice to the guy that has to get up on a ladder and put the titles on the signs outside the theater. After movies like Homeward Bound: The Incredible Journey and National Lampoon's Loaded Weapon 1, he must have needed a break.