Israel, in many ways, is a leftist's dream - universal health care, massive "social safety net", conventionally liberal court system (haven't executed but two people in 50+ years), etc. Iran, OTOH, makes the pre-Colonial puritans seem like progressives. Iran is about as backward thinking on social issues as you can get. And yet, their biggest defenders are "social issue champions". It's cognitive dissonance, in the extreme.
It’s extraordinarily simple.
The biggest hot-button for progressives is not “pro” anything, it’s anti. America, western civ and by extension Israel.
Any person or group that is also “anti” these will draw their support.
The enemy of their enemy is their friend.