A few users do not control the content. Each day, another OP and another commenter gets top position because they deserve it based on their specific knowledge.
Their reputation system probably operates like ours, so I'd guess the diversity of OPs is mostly a function of their size.
I spend hours in recent most days looking for new OPs that have something worthwhile to say/share that might've been missed. We just aren't attracting enough people to have many effortful randos yet. We'll get one every week or so though.
We have a lot of backpressure on growth (participating costs something and the UX of bitcoin), so we some figuring out to do to get there.