It is usually limited by the cache of the DNS server to which you connect (most of the time the one provided by your ISP), so unfortunately not much you can do except waiting, or forcing the address in your machine's host file, but that's not recommended if you don't know how to do it
You can always try both of https://imcdb.org and https://www.imcdb.org as one may be in the cache since longer than the other.
Quickly after the change a lot of bots were already browsing the site.