They are willing to work for less salary. There was no large shortage of Americans, just Americans willing to work for less. After they've come in as managers

They are willing to work for less salary. There was no large shortage of Americans, just Americans willing to work for less. After they've come in as managers or VPs, they get to control who the company hires. That's when the casteism comes into play cause they'd only hire from their own caste or village. I've seen whole teams hired, not in the US, where everyone was from the same village and related to each other. Of course this was only known after one of them accidentally let it slip out.