It's been a trend on more than a few polls that someone decides it's time to be hilarious and vote 50 or so times in a row at some point of a poll. I had it happen at least 2-3 times in 2020, most memorably in the 1980s Movie Tournament when Karate Kid got like 104 votes in 3 minutes.
While it's still not much of a deterrent, Brian, you can make the option of have people enter an email address when they vote. I did that on my first couple of tournaments because I wasn't aware there was another way, and got tons of fake email addresses. But assuming it's just a d-bag voting over and over again and not an actual program, it would force them to keep entering some more characters to make a believable email address.
More than likely it's someone who doesn't like something you said 3 years ago on some random forum that you don't remember and has decided this is the day they gain their sweet pathetic revenge.