From the FAQ (click the headline link):
Q: Why is your website so popular? Are you one of those famous people that no one knows why they’re famous? A: No, I’m not famous. It seems likely that most visitors simply mistype gmail.com and end up visiting gail.com by mistake.
Q: How did you manage to get gail.com? A: My husband registered it as a birthday gift back in 1996.
Gmail launched in 2004. So this domain is OG.
Q: How many times a day is this page visited? A: In 2020 this page received a total of 5,950,012 hits, which is an average of 16,257 per day. Looking at just unique hits, we received a total of 1,295,284, for an average of 3,539 unique hits per day. Occasionally, we get Twitter-bombed and may get several tens of thousands of visitors a day. As an example, on July 21st 2020 we received 109,316 hits.
That’s amazing traffic, all accidental. Fascinating.