The biggest hurdles for each were the bootstrapping into existence.

For bitcoin this happened in say 2010 - going from satoshi alone, to any sort of global use was the biggest hurdle, everything since then was like water running downhill.

For nostr I guess it happened a couple years ago.

Both these are like a spaceship passing the event horizon of a black hole. You don't notice anything unusual at the time but once you've crossed that invisible line your fate is sealed.

Though I think you can argue that both were always inevitable anyway - certainly nostr was. You could possibly say for bitcoin you only had one shot at it, because it has to arise organically / stealthily and when everyone knows what's happening you can't do it. But I think probably over time this would have been got around somehow.