It's not so remarkable considering the IITs aren't a single university. They are dispersed across all of India which is a fairly large country geographically.

Also the fact these three people come from India isn't that remarkable considering that there are 1 Billion people there. Now if they were from some small developing country like say Sri Lanka or Bhutan, it would be really impressive.

yeah, isn't it even quite the opposite, I'd be really surprised to hear otherwise. The startup scene in SF is predominantly white, but SV is nothing like that, pick any large software company and you'll find the split is something like 80% Asian, split with varying amounts between south asian and the far east (india and china/taiwan) with the remaining 20% being of european descent. Whenever I interview for a position, I can guarantee one or more of the candidates will be from one of the IITs. As someone said, with CS being such a strong emphasis in two of the largest population centers of the world, this really isn't very surprising at all. America was and continues to be an immigrant's best opportunity for prosperity with the shift over the centuries from europeans to asians.

IIT as alma-mater gives the engineer an escape vehicle from India. That is partially why you see so many of them at interviews in SV.