So the YouTube channel The Film Theorists just released their latest theory in which they examine whether and how Simba could've survived and grown up on a bug-based diet. They overestimated Simba's actual dietary requirements (all estimates are based on the daily food requirement for captive adult male lions, even though Simba was barely into adulthood towards the end of his time with Timon and Pumbaa), but it still works out fairly well as a result.
Long story short: he could, with some potential health problems: https://www.youtube.com/watch?v=fmRs8HaMRUA