Well, bitcoin was overpriced. I think that the natural range for bitcoin currently from the demand and supply is probably $2200-2500. When overpriced, there will always be a correction. Ntohing surprising. Same with ETH but in ETH's case it was a huge ass bubble instead of just overpriced in bitcoin's case.
There is no such thing
There is no natural range of price for such speculative assets as Bitcoin (it could be said that its "natural" range converges at zero on a long enough timeframe). In this way, any price, be it 20 dollars or 2,000 dollars per coin, is "unnatural" in the sense that it could easily go down as well as go up from that. The good part of this is that we can't say that today's price is the limit. In other words, only sky is the limit (but never forget about the other part)