Top Indian talent did go to the US by default, but that peaked ~10 years ago. Nowadays there is enough opportunity in India - and the US immigration process is bad enough - that most people I know just don't bother. The visa backlog is almost entirely made up of the tech equivalent of minimum wage workers, all sponsored by Infosys/TCS and other consulting firms.

And the "SLIGHTLY below US salaries" part is an exaggeration. Top talent in India is still at most a third of the high-end Silicon Valley rate.