My https://wesleytian.github.io page is redirecting to wesleytian.com, while wesleytian.github.io is non-deterministically giving a 404 error. I removed the CNAME from the repository so there should be nothing connecting my github pages to my domain name anymore.
My suspicion is that the dns is still propagating and will take a moment. How long can I expect to wait?
When I went onto the link you provided and refreshed multiple times(https://wesleytian.github.io), it works and does not give a 404 error!
As for your question, it usually takes no more than 24 hours, and normally, it'll take less than an hour. When I first set up my custom domain for my GitHub Pages, it took no more than 5 minutes for my .github.io link to be connected with my custom domain.
If it still doesn't work on your browser, you may need to clear cache and delete cookies on your browser, or try to go to the link on another browser/device, then it should appear normally.