I think he was pointing that massive dollars have gone for AIDS research but it is not what should be our high priority compared to other death causes. In America and world both, AIDS is small fries for death cause.
The critical distinction is outcomes: until relatively recently, the only outcome of an HIV infection was eventual death from AIDS. This is still the default outcome in most of the world.
Plenty of things kill more people than AIDS, but most of them have substantially less severe individual outcomes: many people survive them, or the social/political solutions are substantially more tenable (healthier eating, access to potable water). And that's even before we consider how AIDS research has advanced the field of medical virology as a whole.