Why does resource rich Africa need to fear sanctions from cacs?
The modern world is built on cooperation unless you wish to live in the stone ages like Cambodia and Vietnam did when they attempted what you are insinuating in the 60s and 70s independent of the world economy.
Resources alone are useless cause you need inputs (both intellectual and physical) to refine and process them. These inputs are globally distributed and specialized. No country on earth, has all the resources within its borders to build modern cars or computers or geothermal turbines. For example, congo has the raw materials to build the previously discussed items . But congo lacks the intellectual inputs processes (refined materials , semiconductors, academics to design, spare parts, patent rights, etc). The significance of the sanctions after the pyrrhic land grab is that any foreign body or individual that gives you these inputs faces their own sanctions .
There are parts necessary to build every modern convenience that are only manufactured by one country and only that one country has the trade secrets and expertise to create them. In order for Africa to even make a car , they MUST trade with Western ally Taiwan semiconductor. (Not optional) . Look at how even the mighty better resourced , EU, US , Chinese, and Russian economies stagnated in absense of this supply during COVID. See how Russia and China still struggle today because of this single part
There are thousands of non-substitutable inputs like this that make trade mandatory. When the west turns off the tap and nobody will trade with you
Btw, what you are describing was attempted in the past by several African nations under "import substitution" and it failed miserably. Tanzania is one example