Successful contributions to open source projects are a kind of currency. GitHub in particular encourages this in a number of ways: by showing avatars of contributors on repository pages, by showing your contributions to your followers via the activity feed and by signalling contributions per day on the activity graph of your profile. Potential hiring managers often take note of this. Recruiters often find and screen candidates this way. If you are a software developer (either existing or aspiring) looking for work, tuning these signals can often work to your advantage.
Are you US based? If so, can I ask how large the companies were? I wonder how much of the effect was HR vs actual programmers looking at a CV. I have never cared about outside work because it’s really none of my business, but I’ve heard and experienced some issues related to it. A lot of people swear that company X won’t even look at an applicant that doesn’t have at least Y projects on their GitHub.
US based, companies between 50 people all the way up to thousands.
HR generally was all about buzz words on the resume because they generally didn’t know what half the stuff meant. The engineers typically wanted a team player, someone who could grind, someone who could just get features / tickets done and multitude of contributions or projects on GitHub always screamed “bounces around between multiple things and never focuses on just one thing and needs to feel constant movement” - which could mean a flight risk.