Right. Cloobeck recognizes the party will inevitably have to move left to be viable. He recognizes Bernie Sanders message is what's popular among the base and among progressives. His threat is towards the Democratic leadership; namely Wyden, Schumer, and Pelosi (the Dem leadership). That if they follow down that road, he will stop funding their campaigns.
"I'm getting what I want from you now, but if you try to raise my taxes, you should look for other donors to fund your campaign because I pay you to ensure my taxes are low. That's your job."
It probably has much more to do with kickbacks Cloobeck and his ilk enjoy outside of lowering taxes the Democratic establishment provides him, as well.
The problem is that very wealthy people have the legal ability to purchase American politicians in order to represent their interests over constituents. Another problem is that smart people like you become so partisan because the opposition is so abhorrent you forget to hold your own team accountable for the exact same shitty political practices you condemn them for. The result is poor people, people of color, women and other minorities feel the consequences the worst.