Why is it also present in Indonesia, a Muslim nation colonized by the Dutch
Please read the Jakarta Method. Indonesia was trying to build up some kind of socialist system after Dutch rule. The democratically elected leader was a member of the Communist party but overall was not forcing a hard revolution. The US manufactured a right-wing military coup that would go on to execute nearly a Million members of the communist party, imprison over a million more, and lead the country down a right wing reactionary path. Indonesia pre-coup was is almost unrecognizable compared to modern Indonesia.
Iran was never directly colonized
The 1953 coup strengthened the shah and changed power to be far more pro-west interests, imperialism in a mask. The later Iranian revolution was again, a reaction to the more or less puppet regime. I don’t think anyone on the left has more than a critical support for Iran to self govern. Of course not all changes or revolutions are a blanket good.
Generally the support for Islam on the left is a counteraction to Islamophobia in the west, where Muslims are written off as terrorists due to the multiple decades of war waged in the Middle East.
I personally know non-muslim brown people called “Terrorist” in predominantly white school districts in the early 2010s. This racism didn’t go away, and it won’t go away by demanding people to surrender their religion in the name of anti-homophobia. Doing so, claiming they’re generally homophobic is the same as generalizing them all as terrorists.