As that one dude said at the beginning (after the guy who looks like Carl Sagan a little bit), the women in this video are not necessarily developers, but can program. At the time, I believe programming was largely done by women...the women would program the computers, while the men would design and build them. But that programming wasn't really "development", per se, it was more like grunt work. At least, this is the impression I get from conversations with my grandfather, who worked with Dr. John Mauchley on the ENIAC computer and helped found the Eckert-Mauchly Computer Corporation, one of the (if not THE) first corporations dedicated to producing computers.

Although ENIAC and such were the official start of the computing industry, the way you interacted with early computers was much different from the way you interact with the UNIX system, and thus, practically everything that's come afterward. So in many ways, this is the real start of the computing industry, to me anyways.