I have always wondered to myself what or where their source of revenue is from, from my personal perspective or observations, not many people use mixing services, and even if there are many who do, can the fees generated from transactions cover the weekly payments of the signature campaigns and for such a long period of time?, this has always been my thought but then..
Your perspective/observation and their signature data statistics are contracting.
It's obvious they are well financed to back their signature campaign ever since they have started. Especially when they start paying by usd rate instead btc fixed for several years.
About their source of funds, there is no proof of them having other business aside from the mixer so probably its their only source.