I have no idea what you are trying to say. You don't appear to have read what I said at all. There is no magic "just be focusing" power. You can't just tell people to stop doing what you want, and start doing what you don't want because some random guy on the internet thinks it will make some random software you don't care about more popular. The netbsd devs don't care about making freebsd more popular, deleting 3 of the BSD lineage operating systems won't make a focused effort on the remaining one, the remaining one would still be right where it is now, and the devs of the other systems would simply not be involved. This would be a loss, not a gain, as the remaining system would no longer have 3 other OSes to pull code and ideas from.

You are doing the equivalent of saying gnome developers should just delete gnome and start working on KDE instead. The gnome developers aren't interested in KDE. If they were, they would be KDE developers, not gnome developers. This is the same with the BSD lineage operating systems. NetBSD developers aren't going to become FreeBSD developers just because you think it would make them do better in a popularity contest they didn't enter. If they wanted to develop FreeBSD, they would be doing so.