Many things are harder, not easier, for large companies than for small.
This is a non sequitur.
It has taken Fairphone considerable effort to arrange these working conditions. It effectively makes their device more expensive, and gives them far less choice on suppliers.
Apple is such a powerful company with deep pockets that they could easily arrange better working conditions for employees of Foxconn if they wanted.
This is a problem that needs to be solved by governments.
Government intervention would help, but I assume not before labour organises to put pressure on the government in the first place.