Is it strange and unexpected that attempted life-extending drugs shorten lifespans as often as they increase them?

The activities of people like Ray Kurzweil, who take literally hundreds of supplements, suggest that this is strange and unexpected, and cannot be deprecated enough. It also particularly cautions us against caring about any supplement or drug without dozens of positive studies (at a minimum).

Or is it disturbing that the drugs are very likely to simply do nothing at all?

That's also disturbing. It suggests - pace Algernon's law - that there is no good simple intervention.

The fact that this is a pretty smooth bellcurve also indicates, as far as I can tell, the general field has found no intervention at all that works - because then there would be dozens or hundreds of studies tweaking it and replicating it and investigating why it works. We don't see a bimodal hump with most interventions at net 0%, and a second bell curve of caloric restriction/intermittent fasting centered at eg. +40%.

(This latter interpretation could be wrong, since the data is so heterogenous. It could be that the apparent excess of studies around +100% represent many of the CR/IF studies.)