If it is so easy for US companies to hire good remote developers en masse from places where it is cheaper to live than it is in the major US tech hubs, then why

If it is so easy for US companies to hire good remote developers en masse from places where it is cheaper to live than it is in the major US tech hubs, then why did US companies not start doing it years ago? Are the people who run software companies so cautious that it took mass enforced work from home to make them decide that hiring cheap developers remotely could actually work? I have some doubts about this. Maybe hiring good cheap remote developers is not as easy as it seems.