Actually they were kapos. The worst, the sickest, and the most sociopathic guys were elevated to block leaders, and Schumer and Soros are the types we are talking about.
The Judenrat was the governing body in the ghettos. Schumer would have been their too, and you are quite correct.
It wasn’t like the Judenrats didn’t end up in the concentration camps a few weeks or months later, and continue doing the same things there.