You gotta remember, despite everything we say, everything we’ve written, the laws in place, the rapidly growing atheism, the US is a theocracy first and foremost. The religion is just as important as the economy, employment rate, or the opinions of the ruling class.

Just speaking as someone who grew up in a hyper conservative cult, I think sowing cognitive dissonance in the minds of religious youth is a great way at getting them to realize they are being taught bullshit. Hearing that Jesus’s views didn’t align with the views that had been forced upon me made me want to read the Bible and make my own decision about God and religion. I started my read fully expecting to end up with deeper faith and ended up crashing out and losing all religious belief, which was my first step towards me being a leftist today. All because of people pushing back on what Jesus would think of religious conservatism.

Considering that the majority of vocal Christians vote Republican, Jesus being very explicitly leftist presents an opportunity to nudge them left. It certainly won’t convince all of them, but there are those who actually value their prophet more than their politicians.
Anyone who cares about diminishing the Republican stranglehold on America should care that Jesus was a leftist, even if they didn’t personally care about Jesus.