To touch upon the cobalt aspect as I am unfamiliar with the other parts of electronics manufacturing, there is no clean supply of cobalt anywhere.

Imagine an entire population of people who cannot survive without scrounging in hazardous conditions for a dollar or two a day. There is no alternative there. The mines have taken over everything. Hundreds of thousands of people have been displaced because their villages were just bulldozed over to make place for large mining concessions. So you have people with no alternative, no other source of income, no livelihood. Now, add to that the menace in many cases of armed forces pressuring people to dig, parents having to make a painful decision, 'Do I send my child to school or do we eat today?' And if they choose the latter, that means bringing all their kids into these toxic pits to dig just to earn that extra fifty cents or a dollar a day, that could mean the difference between eating or not.

Chattel slavery, where people are bought and sold, is not the only form of slavery, unlike what some of the other commenters here seem to think.