Only Fandom staff and soap can delete a wiki. They only delete wikis if it breaks the Terms of Use or the Community Creation Policy.

Thanks

No problem!

I think the owner can delete it, as once I remember it happened also.

They can't. They have to request for a wiki closure through Fandom support.

Sidenote: Fandom owns all wikis; users do not.

Technically if a Wiki Founder wants their Wiki closed that is indeed possible, however as Noon stated they have to follow the same procedure as every other user by contacting Fandom Staff and requesting the closure of the Wiki.

Guys, I have one more important question, would it be possible to avoid the creator asking for the wiki to be removed? Basically, the administrators who take care of the wiki prevent the owner from removing it because they are against it.

Fandom staff aren't going to close a wiki without good reason. If it doesn't break the rules it won't be closed even if the "creator" asks for it to be.

I understand, thanks again!

Fandom also deletes inactive wikis without any prior notice. They have done this to at least 3 wikis I've contributed to and a lot of content was unfortunately lost. These did not break any rules and was a result of low activity despite having tons of useful content.

If you are worried about a wiki being deleted, then create local backups of it, do not rely on Fandom.