Why don't the European countries want African countries to develop, especially West Africa (Nigeria)?

Short answer: they would lose control. Europe likes control. Control of its people, control of the cheese prices, control of the fiscal policy, etc. They also like to think of themselves as the smartest in the room, as the leaders the world so badly needs, and they love to preach to others what others should do. Yet, as soon as their values are tested they buckle like the hypocrites they are. They were comfortable on their high horses when proclaiming that Africa and other developing nations should skip the benefits of fossil fuels and decarbonize in an insanely short timeframe without doing so themselves, and all it took for all their bluster to crumble was Russia closing a few pipes. Now nuclear and gas are rebranded as green and we all have to pretend like this was the European plan all along. 1984-ish to say the least.

Europe does not want Africa to develop, because a developed nation is harder to control. Especially, if giant Nigeria gets its act together and works as one (hard to do due to the tribal divide the Europeans intentionally created when they drew the country lines).

Europe is scared. It has its moment in the sun and it wishes to continue doing so. However, Europe is tiny, resource-poor, and myopically involved in its own history.
Africa is the continent to watch in the next 50 years. We are growing insanely fast as to population, educated populace, and consumer base. Therefore, there is going to be a huge influx of investment and opportunity in Africa, and a massive outflux of Africans on the world stage. This is going to shake up the existing power structures and those in control are scared of losing their yachts and ski lodges.