Even with all the recent issues with freebitco, they still have more than 20M hits per month. Still, many gamblers prefer to gamble there or some may even come there only to claim free faucets but this traffic number is kind of huge especially when you see the complaints and issues faced by gamblers on this platform.
According to similarweb, the traffic on the freebitcoin site for the last month was more than 26 million. For example, the popular exchange bybit has about the same traffic. This is really impressive, but I honestly have doubts about the reliability of this data. Personally, I think that the problems that have been occurring with the freebitcoin site over the past year should have triggered an exodus of most of their audience.
How does Similarweb calculate website traffic? Does Google Analytics sell them some data? As far as I know, it's against the rules but I wouldn't be surprised if Google Analytics sells them because they are shady. I think that the only other way for Similarweb to collect data is if website owners connect their Google Analytics to Similarweb apps but I doubt top websites do that because it's not a good idea to share their data for nothing in exchange.
I think that another source of traffic estimation for Similarweb will be through adware extensions, browsers, softwares and VPNs but how accurate is that? I can't imagine 26 million people visiting Freebitco for gambling when there are so many issues around them. I also can't imagine two men taking care of the website with such a huge traffic.