I come from a very progressive family that always tried to treat me and my sister equally. Still, I think there was a much larger social pressure on me to be financially successful than my sister. And that is in a very progressive country, too, in more conservative countries the effect is probably larger still.

I do not know how to calculate that. At least few stem fields have very high number of women, medicine for example. So why more women do not choose mechanical engineering, hard to say. It is not because these fields are dominated by men. Women were not dominating medicine, but now they do. So clearly women are not afraid of taking up fields which are male dominated. Women are far more courageous than that. Women also dominate HR departments of many financial, software, and other industries. So clearly they work in the same industry as men do, just in different roles. So why they do not choose to be engineers in these companies instead of HR person, I have no idea. All I am contesting it, it is not because men have an invisible alliance to stop women from doing so.

My gut take is that our society is socialized to value men that have some sort of "breadwinner" status.

Not just society, but women especially. It’s not even an issue of socialization. Unemployed or underemployed men are heavily penalized in the dating pool. You don’t have to be a gold digger to value a stable provider as a partner. And women who are self-sufficient still generally tend to prefer men who are at least roughly equal in their ability to provide.

Because men have more options for careers that provide an upper middle income lifestyle in India than women. Tech is one of the few that women have access to that can provide that.

Could be a lot of reasons.... if STEM majors have a 'bro' culture, then more men would feel comfortable in that culture than women, and would not be driven away from it.

will bro culture explain women not enrolling to these majors or just dropping out of these majors? My guess is latter.

The hypothesis is that when economics are less of a factor, people tend towards work they find more enjoyable. Men control most of STEM, so it sucks less for them, which is why you see women disproportionately leaving.