AI researched and produced nukes

For context, My friends and I created a private historic world war game and since there wasn't enough of us to fill all the slots we left some playable countries empty, e.g. Brazil. Now, on day 32, I flooded Brazil with spies and discovered that he was building a nuclear bomber level 1 in one of his cities (Sao Paulo). Brazil was an AI for the entire game since none of my friends joined as him and nobody disturbed it until now.

I've read somewhere on the forum that AI do not research or produce nuclear weapons unless a player already had them in the first place and then went inactive. In that case is what I'm experiencing normal?

I've attached a picture of it.