Umm while yes it takes a long time to write a novel, the title isn’t exactly correct. How you publish mattering on where you go isn’t a long step. I have only done self publishing but I don’t think the publishing houses take that much longer.
Take Amazon for example and e-books. I have published a few e-book short stories in my life time and it takes about half a day if they don’t detect an issue.
Pretty much to publish is to take your finished product and get it into stores and sell it. It isn’t that big of a step that takes weeks.