If the split happened to be 80%/20% or 90%/10%, then no one would complain even if the author was pocketing $1M/mo. In fact, I and many other people would likely be ecstatic.
However, knowing the actual split, and knowing that the majority of funding didn't actually go to developers, it's a lot more difficult to make the social argument at this time. It necessarily falls back on the practical question of whether it is effective to advertise in the READMEs. Most of the previous sponsors were drawn into the social cause but not necessarily the practical effectiveness of the ads themselves.
Even though it's not a charitable cause, they are trying to make the same appeals. And if a charitable organization was eating away more than 50% of the donations in administrative costs, you would likely be very wary.