I agree with you that it seems he died of illness and his "family" is covering it up...and while I personally find Conspiracy etc to be a bit much in this situation (he wasn't really influential in huge numbers and not a threat to the powerful medical/pharmaceutical system/companies) but anything is possible.
I just think there are more influential targets for that. I think Andreas didn't have enough of a following to be a target.
That said...anything is possible and though my thinking is more in alignment with yours, it's still important to have a respectful demeanor regarding other people's mode of questioning and their ideas. Far-fetched things do actually happen and I don't think this is one of them—though I'm sure Andreas' wife would like to have people believe that!