It’s a lot cheaper than medical school, and you have a parnassah four years after starting. It also requires a lot less of an investment in time to meet entrance requirements. Especially since frum Jews don’t like being touched by members of the opposite sex, there is a high demand within our community for male nurses. The hours tend to be better than doctors (e.g. never “on call”, flexible shifts). Especially for a Ben Torah, the ease of entry to the career and the rules of employment are an attraction. It pays a lot better than teaching in a yeshiva, and you can still arrange shifts to learn.
Given the aging of the population in America, there’s a good long term demand, at least for fully trained nurses – meaning a B.S from an accredited university (excluding some “quickie” courses designed within the frum community).