why did it take so long for christopher nolan to release the dark knight and released it in 2008?

He made movies between them. After Batman Begins he made The Prestige, and after Dark Knight he made Inception. That means Nolan made five movies in seven years, he probably makes movies more frequently than almost any other filmmaker.

Well, it takes time to find shooting locations, shoot the film in one location, shoot the film in another location, shoot all the scenes in no order, then take the time to edit all the raw footage, bring it down to a set time length, re-shoots, re-edits, finalize it to make sure it makes sense when watching, make trailers, and then release it.

Not every director and/or producer can just make movies and release it on the fly. The Tobey Maguire Spider-Man series, The Matrix, Rush Hour, and more are the same way

You realise that these kind of movies don't just get spit out and made every year right? A good spacing between the movies in a series is great, it makes people want to watch them more.

Meaning everybody should make movies to satisfy you?

Get over yourself.

You obviously have no clue how movies are made.