Those are automated registrations... those are bots... those are not humans who are viewing the page and then enter a random username by flicking their keyboards randomly... these are bots... there are not humans... these are programmed scripts that do a specific function.... these are not humans... these are bots...
p.s. these are not humans...
My apologies if I had to bludgeon you with the obvious

Why are they the same? Coz they're using the same bot script - which obviously would generate the same "random" usernames ... if not, law of averages take over...
Why are they doing it? You mean, other than to
spam the forum and generate hits? You got me there...
Are you looking for the
correct explanation, or are you looking for an explanation that
you can accept? Coz those are two different things... let us know what answer you want, and maybe one of us can humor you...
And by the way:What I quoted is the correct answer... if it's not the answer you want, then stick around some more and someone just might come up with a conspiracy theory more to your liking
- T