Common sense?
The Argentine govt agencies have the capibility to drop a man onto the roof of one the most heavily protected apartment buildings in Puerto Madero (he had 10 close protection officers under his personal control, and his own firearm), enter detected by man, dog nor security camera, kill a man in his bathroom positioning the body to block the door, requiring a locksmith to open the door from the outside as it was locked internally?
It's not within the realms of possibility that either he didn't have the proof and crumpled under the stress of his upcoming public shaming or more plausibly he had just discovered that the proof he had was fabricated and handed to him by a disgruntled ex SIDE agent. Perhaps another source confirmed this and he realised he just went full frontal with fabricated evidence. End of career, public embarassment.
To me both of those are plausible, as is a highly competent govt or Iranian assasination. It's just that highly competent, impeccably executed (poor choice of word) govt operations don't see to fall within my defiinition of common sense.
All possibilities and motives exist, churlish to rule anything out based on what you've heard or read.
...and now I'm speculating too. Internet 1 - Magico 0. Bah.