Personally the idea of partying next to Gaza is abhorrent. Not everyone shares that view, and whatever your viewpoint, you're supposed to go home hangover after a rave, not in a body bag. But if you asked most left leaning youths I don't think they would go, given the location.
It's feasible. Is there any evidence most of them supported peace with Palestine?
A lot?
I was looking at the breakdown of members of the Knesset. A sliver of members are left leaning. Are the left leaning Israelis just not voting or making their views known?
https://www.timesofisrael.com/the-israeli-left-has-lost-more-than-an-election/
And since when did raves have leftist/right leanings? You go, pop molly and jump to EDM, that's done by young people across the spectrum.
At this point, its a stretch to assume the crowd had leftist leanings.