They do want a communist country -- BUT with THEM being in charge of the Politbureau. They do NOT want a scenario which risks them NOT being the ones in charge.
The rich giving to leftist causes are what Lenin called the “useful idiots.” They will be the first ones disappointed with the revolution and, therefore, are the first to liquidate after the revolution to avoid them becoming a counter revolutionary group. Pol Pot put this to practice and murdered the educated after he rose to power.
Bernie certainly puts them in that risk
His radicals would have zero problems taking out the current bureaucratic establishment