As a true amateur,I don't understand the basic premise of this extremal black hole mystery. In my simple view, if a charged black whole is extremal and cannot

As a true amateur,I don't understand the basic premise of this extremal black hole mystery. In my simple view, if a charged black whole is extremal and cannot shrink then... the solution simply is that it must grow again. It absorbs particles of the opposite charge until it becomes neutral enough to shrink again and the process repeat until it completely evaporate. That seems both a simple and straightforward theory. (Then my other misunderstanding is how a black whole would become so charged when the universe is seemingly so neutral. The law of big number ensures that a black hole would be mostly neutral and the extremal case would only happen for very small ones on the brink of evaporation.)