Why the hell Joker wants to destroy Gotham city. I know that he is insane, but he does everything with an intention. Whats the motive behind he wanting to destroy Gotham City?

It’s not just Gotham , he has destroyed many cities buthis real motive is to see people turn into monsters for their lifes
The current ideology of joker is that society is worse than weapons

So Joker doesn’t want to destroy Gotham in general. See, mindless destruction is not Joker’s True intention. Joker’s ideology is this(and please don’t mind if I sound like Heath Ledger Joker): He believes that everyone wears a mask and PRETENDS to be civilised. He thinks that all the good in people is a lie and they are fooling themselves by telling themselves they are good people. He wants to push people, to put them in life threatening conditions so that they can show, what Joker believes, their true nature. He wants to kill people so that he can instill the feeling of revenge in their loved ones.
This is the PHILOSOPHY OF JOKER which ricochets across all the movies and comics: “YOU’RE JUST ONE BAD DAY AWAY FROM BECOMING ME(JOKER)”. Hence he takes any means that’s necessary, even if it’s destroying an entire city. He once did nuke Superman’s city Metropolis, hence turning Superman into a murderer, which kinda proved his point.

But I don’t think Joker would destroy Gotham, because Gotham is what Batman fights for, and Joker doesn’t want to put down permanently, cause after all he(Batman) is his(Joker’s) greatest amusement.

Please ignore any typos. I am typing it on my phone.

he wants to make everyone crazy