RMRK has been a bit slow in activity for several years now, with little bursts here and there, but I think the biggest reason it became so dead is because registration was closed for so long. It's painfully obvious if you just look at the stats. We went from getting 1000+ members one month to ~400 to 92 and then none. Nobody joined in April last year and it was several months before new members even broke double digits. So while older members may have been moving on like they just do sometimes, we weren't getting much at all in the way of new people.
This just made the forums look dead and unappealing to anyone who would have thought about joining later, so even after registrations were open again, our numbers are severely lower than they used to be.
So while I don't think the lack of focus on RPG Maker over the last several years has been why RMRK declined in activity, it's probably the best way to increase it. And that's something I fully support. I mean, the name RMRK is totally unfitting as it is, so we might as well fix that. Though to be honest, I don't think we'll be able to boost activity all that much at this point. And personally I don't think there's anything wrong with that. Maybe that's because I'm much busier than I used to be and I don't have time to stop by here as often.
Anyway, that's my point of view on the whole thing.