You're saying that the NATO bombings and the NATO-backed rebels had nothing to do with it..? He was fleeing a NATO air strike.

Yes. Gaddafi was also certainly killed based on French intelligence, and there is substantial evidence that the men who assassinated him were French assets. Part of the reason, apart from the broader geopolitical aim of annihilating a country which wanted to engage in the construction of international monetary and commerical systems outside of the orbit and control of the American petro-dollar, Gaddafi had essentially bribed Sarkozy at a certain point and was holding this over the latter's head (Sarkozy is infamously corrupt). See:

• https://www.mediapart.fr/journal/international/021012/gaddafi-executed-french-revelations-libyan-agent
• https://www.middleeasteye.net/news/french-secret-service-killed-gaddafi-sarkozys-orders-reports
• https://www.rfi.fr/en/africa/20121001-french-spy-killed-kadhafi-sarkozys-orders-papers-claim
• https://www.dailymail.co.uk/news/article-2210759/Gaddafi-killed-French-secret-serviceman-orders-Nicolas-Sarkozy-sources-claim.html
• https://www.euronews.com/2018/03/20/sarkozy-in-libya-case-what-does-it-all-mean-

Hegemon's have to rule by fear. Read any bloodsoaked page from the history of the Roman Empire. Fear is best instilled through unimaginable atrocity. What do you think the rulers of the rest of Africa and the Middle East thought after they saw how Gaddafi, head of the most prosperous (per-capita, quality of life, standard of living, etc.) state in Africa, ended up?