IIRC he had some kind of insurance file against that, I think there used to be some encrypted file you could download from Wikileaks and if he died the password would be released.

No idea what it was (if anything, it could have just been a bluff of course) but it seems to have had the desired effect so far.

As a terrorist they could torture and kill him without covering anything up.

https://www.abc.net.au/news/2021-10-01/julian-assange-supporters-write-to-pm-over-reported-cia-plot/100504522