Natural selection tells us the process typically works in the reverse order: environmental pressures create a situation where the emergence of increased intelligence grants the individual an ability to leverage the calorie source to their distinct reproductive advantage; not just relative to lions but relative to those in their group. So the marginally improved intelligence mutation occurs first, and it has to be so advantageous that it can overcome counterveiling selective pressures such as more aggressive individuals simply taking the calorie rich source. Were it otherwise we'd be living in Planet of the Apes, or more likely would never have existed.
Whatever evolutionary strategy our ancestors found themselves pursuing, it almost certainly must have been unique and special. The notion that we developed intelligence because intelligence intrinsically provides a reproductive advantage doesn't make any more sense than the notion that we developed intelligence because we could eat fat. Such simple strategies are immediately, incrementally, and perpetually available to countless species, now, then, and prior. If it were true it would imply that evolution is a simple escalator for traits like intelligence, but we see no such evidence of that.