Bitcoin is not a currency, but a greater-fool speculative token, that is, something that you buy at price X (you fool!) with as a goal to sell it for something like 20 X to a greater fool.  It was designed that way, even though people called it a "currency".  Like with socialism, greater fool games stop when you run out of greater fools.

But greater fools come in armies.  A small set of geeks got in in 2011, financing the gains of the very very small fools that had been heating their computers in 2010.  Then it crashed a factor of 10.  In 2013, a much bigger army of greater fools financed the gains of the hodlers of 2011 and 2012.  Then it crashed a factor of 6.  And last year, the "Koreans and Japanese" financed the gains of the hodlers of 2013-2016.  How low will it crash ?  A factor of 5 ?  A factor of 10 ?   We'll see.
The question is: is there, in this world, still a bigger army of greater fools ?  There's still the whole speculative finance market to take, but beware, these are professionals!   Bitcoin has only reached a fraction of the world population.  There's maybe still room for a last big final army of greater fools, but it will take some years.

As to "bitcoin is not the absolute monopoly", this is true, but the market is REMARKABLY synchronized.  It is as if the whole of crypto was essentially a single token.  Bitcoin has remained around 33-35% of market cap during all this falling of 60% or more, give or take a few percent.  So there seems to be one single "crypto" thing out there for greater fools.

We will see.  I table on at least 3-4 years of bear market.  It might be the final one.   But I table on a very, very big bang in something like 2021 or so.
If we go below the previous ATH, that is, $1200, I think it is done.  If we remain above it by a factor of 2, I guess we're in for a long, cold winter, and in a few years, another mega bubble.  Probably the last one.  There won't be greater fools left after they've paid for the whole shebang.