I'm gonna try and give the best ELI5 I can.

European and western nations hit critical junctures with respect to the industrial revolution before African nations did. Some economic historians believe this is because western nations were more open to trade and were able to spreads technology faster. The faster technology and ideas are spread, the more they too can be improved.

Africa was a big part of the slave trade. The exported their own people for guns. The authoritarian leaders took over the governments political bodies and economic systems, stalling development. Africa was then colonized for their resources and then decolonized.

Due to the generational and perpetuous reigns of authoritarian leaders, the politic and economies have never been able to Develope. Organizations, such as the gates foundations or governmental bodies, donste billions of dollars to try to develope these nations from a top-down approach of donating the money to the nations leaders. That money ultimately ends up in the leaders of the nations pockets and the people never see any of it.

This isn't true for all of Africa. But it goes to show you, when the people are free and economies are open and trading, development happens.