A possible explanation is that men, in the aggregate, are more motivated by compensation and willing to put up with more hardship or danger in exchange for more money.
There are a lot of jobs that pay a lot of money because they're dangerous, like working on an oil platform. Suppose those people get paid $90,000 whereas below average tech workers get paid $70,000 and above average tech workers get paid $100,000+. If you're a below average male tech worker who is in it for the money, maybe you take the oil job instead for the extra $20,000/year. The equivalent women take the $70,000/year non-dangerous job, causing the male average for "tech jobs" to be higher than the female average.
It's also possible that more men than women are willing to work longer hours or jobs with less flexible hours in exchange for a higher salary. Employers rationally pay people willing to do that more than people who aren't.