what does "mostly Bitcoin" mean?

"the market accepted both bitcoin and monero, but in my assessment most of the vendors were doing business is Bitcoin?"

it's true there aren't any hard numbers on TX volumes, but even a cursory glace at DNMs over the last 5 years shows the preference for Monero.

I'd say that White House Market beginning as a Monero-only market and rapidly becoming the dominant DNM (after Empire exitscammed) was a watershed moment.

what was that? ‘21?

since then, except for hydra there haven't been any large Bitcoin markets.

its still used, but less and less because the friction of unloading monero is often LESS than the friction of coinjoins or swapping UTXOs and worrying about the exchange flagging you.

but it depends on the person's situation and threat model of course.