> so does anyone knows whats imdb popular tv shows list based on??

It's based off recent activity. This is why Velma is 20, even though a year from now I doubt many people will even remember it existed. The fact a series that ended 16~ years ago is still that popular is beyond impressive.

> while i've never seen anyone watching it or talking about it..

Beyond that, all these things change over time. It would be weirder if the series was still growing/had an extremely active fanbase after the only content added to it in the past decade was the poorly received movie.