I don't think your initial comment that you considered 300 public votes for Eden Golan 'shocking' is antisemitic. Whether that shock is due to you not liking her song or whether it's due to your surprise that so many people either don't agree with you over the war or are happy to vote for a song they like despite their political beliefs.
@InTheUpsideDownToday 's answer that they were 'bot paid for votes' is antisemitic. As @YaMuvva pointed out, it's pushing very old anti-semitic tropes of Jews a) controlling the media and b) being greedy thieves.
I suspect from your later answers that you didn't even notice that. These tropes are so embedded that people often don't. Try to think of some insulting assumption which people make about some other ethnic or minority group without thinking. Tropes change over time, so I'm sure you can think of one which you're sensitive to but not the whole population is. Think of how some behind-the-times people don't even realise that they've said something outrageous because that picture is still part of their internal narrative. And then think how insulting that is to people in the ethnic/minority group who notice it because it's wrongly assumed about them every day. That's what is happening here.
You answered "Just Depressing" to @InTheUpsideDownToday 's antisemitic post, which implied that you agreed with it. That may not have been your intention, but it reads as agreement.
People on mumsnet often conflate the poster who made a comment with others who agreed with it, since we all read the thread once as a conversation and don't know the posters as individuals.
Maybe you don't believe that Eden Golan's high public vote came from bots or some other unethical way rather than individual fans deciding for their own reasons to vote for her.
Or maybe you have a specific, verified reason for believing that they do come from bots, which doesn't stem from your underlying assumptions about the Israeli government/Jews. Such that with the same proof as you currently hold, you would have believed the same thing of Lithuania if they had a higher than expected vote.
If so, you could (if you choose) clarify that and it would be clear that you were not in fact supporting antisemitic tropes.