What happened to qualudes?

The persons name who is responsible for the elimination of Qualudes in the USA is Gene Haislip. In the early 80s as assisitant deputy director for the DEA he initiated a program of attacking the global trade in methaqualone by eliminating it’s source compound that was manufactured in the USA. Problem solved.

Is it particularly difficult to make?

Methaqualone is a hypnotic/soporific (where the name “sopors” came from).