Wikipedia is surprisingly sparse here.
Edit - in 2012 he was the prime suspect to the killing of his neighbor as mentioned here: https://news.ycombinator.com/item?id=27609243
Drugs.
https://nymag.com/intelligencer/2016/09/the-obscure-legal-dr...
"He was already facing a suit from a man who had tripped on his property in New Mexico. Another suit alleged that he was responsible for the death of someone who crashed during a lesson at a flight school McAfee had founded. He figured that if he were out of the country, he'd be less of a target. And he knew that, should he lose a case, it would be harder for the plaintiffs to collect money if he lived overseas." https://www.wired.com/2012/12/ff-john-mcafees-last-stand/
Wired suggesting it was a financial move is just lowbrow journalism.
(You're roughly correct about the circumstances - his nephew was illegally piloting and crashed a plane killing himself and the passenger in McAfee's low-altitude flight program.)
Guess Belize are lax on experiments and "labs"
https://en.wikipedia.org/wiki/John_McAfee#After_McAfee_Assoc...