Hatred towards the ultra-rich is not based in jealousy but in a moral stance. The argument is not "I want your 30M" it is that "people having this much wealth is bad for all of society".
See: https://www.nytimes.com/2019/02/06/opinion/abolish-billionai...
There's much debate to be had over where that line of "too much wealth that it can't possibly be moral" is, but this is where the cultural conversation is. You're missing the point if you think it's jealousy.
As an example, I never plan to have more than about 2M (in today's dollars) of personal wealth. I'm not supporting this tax because I want the 30M, I'm supporting it because I think it may have positive effects on reigning in the human instinct for greed by aligning societal incentives with personal ones.
I'm trying to keep this narrow as I'm not trying to claim I'm correct that this specific iteration of the tax will work, or even of the form, but hopefully my point about the targeted issue is clear!