Network effects also in terms of merchant adoption among a dozen other things (legal tender, institutional adoption as an asset class etc). Of course you can play your darknet market scenario and hopefully Monero will never disappear but #bitcoin shows adoption growth rate at a much larger magnitude than monero.
Discussion
Monero is hardly available anywhere to be bought easily unlike bitcoin and many other coins. This is by design. But why?
Institutional adoption seems like it could become a reverse trojan horse imo
Maybe we need both to shake things up. Regardless, will be interesting to watch it all play out.