Do you have a source for this? I follow OpenBSD quite closely and this is news to me..
https://www.csoonline.com/article/3250653/is-the-bsd-os-dyin...
My concern (and the concern of many others, I think) is that if OpenBSD suddenly got enough attention from the wider security community, including people who actively look for holes that can be exploited, there'd be plenty of important stuff found. Until then, these issues sit quietly waiting for a malicious party to discover them. There's quite some fanfare for OpenBSD, but how many of you are actively auditing the code? I'm subscribed to cvs@ and tech@ and I read them daily and I just don't see much contribution at all from outsiders. And when I do see it, it's mostly stuff like fixing typos or amending man pages. All the commits that change code with security implications tend to come from the core developers, and are reviewed by a handful of people at best. And I have seen some obviously broken stuff slip through.
This seems like a structural advantage to less popular software. If your software is less common, attackers will have put less time into exploiting it, and therefore you will be more secure. My impression is that MacOS and Linux both benefited from this relative to Windows for a long time.
In general this should be true if usage grows faster than security resources for popular system. It might be still be true even with significant, commensurate investments in security while you grow, because if a small percentage of users mis-configure the software and create vulnerabilities, that population will hit a critical mass with growth regardless of your security efforts.
Maybe connecting everything to a network and making it a high value target by collecting everyone's data is just a terrible idea in the long run.