And I'm sure many men simply did not consider the possibility of a career in female dominated professions, like nursing or elementary education. I think there's certainly something to the idea that we internalize stereotypes and that can restrict our options, but I'm skeptical that it generally explains large differences in career preference today.
For example, women were once stereotyped as not being doctors or lawyers, but that didn't seem to stop them from joining those fields en masse. If internalized stereotyping didn't matter enough to stop them then, for those fields, why does it matter now for engineering?