Sometimes it's easier to take people you trust and task them with a platform that they have no knowledge of. Sometimes that works, but rarely. Mostly due to the fact that if there's no vested interest in progressing the platform there's little interest in managing it effectively or building the relationships necessary to network it. I get to say this because I've been asked to do the same and I watched as the same thing happened-nothing.
I could break this down much further than anyone would ever care to here, but let's just settle on the fact that site ownership is basically a business and there are many 'business owners' out there. I don't know if Zach owns other sites, but I know the owners of the other two sites and they do. I've watched and evaluated how they establish, promote, and run different sites to get better insight on factors that help make or break forums.
As an example, if you count each vendor listed on this site and compare it to those on .org, you'll see that we're 'lacking' in the physical number. Conversely, there is significantly more vendor participation and overall platform progress here. There's a reason for both of those that aren't exactly the same but are related. If you want to make it more interesting, screenshot the vendors on .org and compare the list to those on FocusST.org...the results shouldn't be surprising.
There are other certain relationships and non-helpful mindsets prevailing, which is why Mountune (only as an example, I have plenty of others as well) has such a drastically higher post count on .net compared to either of the other two sites. A lot of people want to point to certain aspects (vendor numbers, 'true enthusiasts', etc.) as to why a site is 'the best', but only site statistics can tell you which ones are legitimately the top performers.
That's a brief overview of an easy yet overly-complicated business. Competition is literally everywhere, so establishing a site and keeping it moving/progressing is not necessarily a small task. It's been fun (and also extremely irritating) watching the three of these sites progress, from a site-management perspective at least.