Secondly, because the people who are in a position to do such research are less likely than the general population to believe in an afterlife.

On this particular point, I would say that people who are in a position to allocate funds for research programs are probably about as likely as the general population to believe in the belief in afterlife.

Generally, I agree - it's definitely not the only problem. The USSR, where people were at least supposed to not believe in afterlife, didn't have longevity research as its top priority. But it's definitely one of the cognitive stop signs, that prevents people from thinking about death hard enough.