Those sites are probably a scam. I'd setup my own botnet if I wanted to rig any contest like this. Keysight didn't even use a captcha.
Honestly I think scope month in general was a fraud. IIRC we had one person "win" on the eevblog. That person complained about paying taxes and in the end rejected the scope. Also funny how he registered on the forum the day he won, claimed the contest was marketing BS, and then deleted his posts. Sounds like a conspiracy to me.
If Keysight really sends scopes, and if the "winners" even exist, then there's really not much you can do about illegitimate voting schemes.
Honestly though, even if you did not have the eevblog army, you should win because the other videos are abysmal. Most don't even have a lab worth $200 and claim that they need the 6000x? Wtf?
Hi (Justin, maybe?), the winners are real, the contest is real, and everyone who was drawn was vetted after the fact to make sure it was on the up and up. We did draw the name of *one or more* winner(s) who cheated the system and their scope(s) were re-drawn.
I really wanted to make them think they won and ship them an empty box with a copy of all their entries, but that probably would have been in poor taste.

We plan to post pictures of the winners with their scopes in the coming months, but there's always going to be some conspiracy theories, etc.