Israel doing well in Eurovision is a completely predictable result of the boycott. The people who are watching & voting in Eurovision are now at best willfully ignorant and apathetic and at worst actively pro-Israel, meaning there will be a disproportionate amount of people willing to vote for Israel and even people voting for them because of the boycott.
But saying that means that boycotting Eurovision was the wrong call completely misses the point of the boycott. The point is not "Israel should not win Eurovision", it is "Israel should not be allowed to compete in the first place". The point of the boycott is not to give the EBU views or money, so if you've been boycotting... don't give them money or legitimacy by voting for someone tomorrow to prevent Israel from winning. If Israel does win, that does not mean boycotting failed; it only further delegitimizes the competition and confirms we should burn the whole thing down.
If Israel ends up winning, that's the EBU's problem, not ours.
Don't watch, don't vote.