They could have abducted or blackmailed him but killing him like that makes no sense from an investors POV, they get nothing back and the risk of getting caught.
They get him dead, which can enough for some particularly evil people with a grudge.
Look at e.g. (probably) the FSB poisoning Litvinenko, six years after he fled to the UK. After six years there wasn't much to gain for the FSB other than making an example out of him and retribution.
Yes but this is diferent though. Those were ex spies who “talked” and wanted to send a message to other spies as in “if you talk we’ll find you anywhere”.
Hope he will get justice