This is from Wikipedia:
Gilligan's Island is an American sitcom created and produced by Sherwood Schwartz. The show had an ensemble cast that featured Bob Denver, Alan Hale Jr., Jim Backus, Natalie Schafer, Tina Louise, Russell Johnson, and Dawn Wells. It aired for three seasons on the CBS network from September 26, 1964, to April 17, 1967. The series followed the comic adventures of seven castaways as they attempted to survive on an island on which they had been shipwrecked.
As you can see, first sentence says Gilligan's Island is an American sitcom. Then it goes to past tense, and says "had" ensemble cast and "followed" comic adventures.
How do we decide when to use past or present tense? It seems strange to me to do it like this: in my own language, I would always use present tense even if the object is in the past. So I would say
Gilligans Island IS an American Sitcom. The show HAS an ensemble cast. The series FOLLOWS the comic adventures ….
I would do this even for dead people. E.g, Wikipedia page on Genghis Khan says he WAS the founder and first Khan of the Mongol empire. I would say in my language he IS the founder and first Khan of the Mongol Empire. Him being dead, doesn't mean him founding the Mongol empire is no longer true.
Similarly, just because Gilligan's Island is over, doesn't mean the show itself doesn't have an ensemble cast or follows their comic adventures... all those things are TRUE even TODAY, even though they are in the PAST. Hence we should use present tense.
So I'm kinda confused about how this works.