"wildly popular"? maybe there was alot of interest when it was released, but who even is still using R1 these days? i previously utilized it through perplexity but the o3/Gemini pro models are so much better i rarely bother to read its responses.
V3 is number 5 in your list. R1-0528(free) is number11 and R1(free) is number15. Openrouter separates the free (in the top 20 list you shared) vs paid (further down) instances of V3 and R1, and of course it doesnt count the direct connection to the providers, or the various self-hosted solutions (choice of companies working in sensitive areas, including many of my friends).
it's not even in the top ten based on OpenRouter https://openrouter.ai/rankings?view=month