I mostly agree with you and I am also rather optimistic for the future of Nim. The community is tiny, but composed of truly motivated Nim users. My remark about the small number of Nim users in Project Euler was there only to give true numbers, and yes, Nim is certainly a marginal language here.
As regards AOC 2018, I’m sorry :-) but the reality is a bit different that what you think. There are 118 registered users on the dedicated leaderboard. Only 98 have solved at least one problem. Others may be Nim users, but have not participated. Now, if you look closely at the solutions when they are available, you will discover that some competitors have used exclusively Nim, some have used Nim and another language, and some have not used Nim at all. For the latter, they may be Nim users, of course, but they have used another language for AOC. And if you wanted to compete for the first places, it was better to use an agile language which you master well. The 118 users who have subscribed are certainly interested by Nim. And some who were only experimenting with Nim have done very good remarks about the language. But you cannot say that there are 100 true active users. Of course, there are certainly Nim users who have not subscribed and have used Nim to solve some problems. Who knows? For sure, it is difficult to have a good idea of the number of active users of Nim. For now, there are private users as me, contributors who write packages and libraries, and the development team. Nothing surprising, I think. Nim is still in incubation phase.
