I have a few theories as to how this happens, but they are all pretty much scandals for Rumble. The options I can think of are:
1. They count total unique connections that make requests on that page as unique viewers. That would be a 20-50x inflation of numbers.
2. They add to the counter when a new IP connects, but don't subtract until a very long timeout occurs, causing everyone on a cell phone to be at least 5-10 "viewers."
3. They use some sort of tracking cookie that has a major bug. Rumble has stored a cookie on my (logged out) computer, so this is a possibility.
4. They are fudging the numbers, probably with some linear scale factor or a more complicated formula (not just a constant).
None of this is particularly good for the company, but counting users is actually kind of hard. The YouTube viewer count is likely pretty accurate because it uses Google's hyper-invasive and very accurate tracking system, but Rumble is definitely far off.
It may be time to do some experiments... especially if anyone has other theories.