Atlas was a diesel forum because that is what the company offers. Over time, that restriction will impart a flavour to the culture there, and by extension to the forums. If they found it hard, or were reluctant, to moderate their forums more assiduously, it should be no surprise that as time went on some people felt they owned the place. If you go to anyone one of about 30 MRR or RC or sewing forums, you'll find the same hard core of about 40 regulars who develop their own clique. If they are to get along and to unify in any way so that they can talk without snipping at each other, they must all slide their bums one way or the other along that loooong communal bench they try to warm each day. They become like-minded, adopt common currencies, such as language and interests, and away they go. Good luck to interlopers and newbies. Those types of places are easy pickin's for trolls, though. Just toss in a stinker or some kind of bait, and go get a coffee.
I will miss that forum...I checked it daily. It had its faults, but which of them don't? One thing is sure, money is a bit tight, but also they just couldn't direct someone to moderate that forum more closely, which it needed often.
Fortunately, there are other very nice places to be, including this one. We should be (at least I am...) grateful to the people who run this forum with any role in its administration and monitoring. As a former moderator over at Model Railroader, I can tell you that I wasn't doing it for my health, but as a service to those who wished to participate free from harassment and trolling. If the hobby is to stay healthy, it needs its watchers and gate-keepers who pass on the good values that got the hobby to where it is today. Judging by the flow and tone here, our watchers do a very good job.