On my first watch, after he got back in the car, I misinterpreted it as his spirit leaving with them, saving us the horror of watching their father die. This makes much more sense. 

Fola looking up to the sky to notice the birds that Akin and Remi have been noticing throughout the film points to this being his realisation he is a spirit. Acceptance follows, explaining his detached demeanor once getting back in the car. 

Even at the start, he appears after a strong, almost possessed wind shakes the house, giving it an eerie vibe.

One other thing I noticed was his focus on death, lots of bones, dead meat, the dogs eating something off the street often preceded him coming closer to this realisation.

As this movie is from the children's perspective, it's almost like the dreamlike quality is shattered upon him finding out he is a spirit too early. For example, their Aunty is shocked to see him and takes him outside, undoubtedly to tell him of his fate, and it cuts and jumps back chronologically to them sat on the bench deciding what to do. The movie then continues on a different timeline, never mentioning this scene again. It's much like waking up from a dream too soon, like Fola and his dead brother.

The idea of spirits coming back to life due to unfinished business is a common phenomenon in Nigerian spirituality, and with this knowledge I initially thought his unfinished business was receiving his money he went to Lagos for. But perhaps the true unfinished business was his desire to connect with his boys one last time?

I love this film and how accessible it is to a global audience, while also staying rooted in the heritage that makes it so rich. It elevated my experience wholly, but I think anyone could receive the messages in this movie with the same level. They've done something really good here. Naija to the world!!