Bitcoin has really failed to overthrow the banks and the state. And that is because everything we do including our business activities are being monitored and regulated by the state.
No, it is because it was badly designed, that's all. Bitcoin contains several fundamental design issues. The most important is ironically what it is touted for to be important: its emission curve, sending out a lot of coins in the beginning, and going down to zero. That turns bitcoin not into a stable currency, but into a speculative asset.
It's not fully about stability, it's about safety. The idea is that
as long as people hold their coins, cryptocurrency's value stays the same or goes up.
If Bitcoin ever has a significant role in society, these "design flaws" won't matter as it won't have dramatic drops anymore. The higher liquidity than being a speculative asset can bring can actually keep it stable, like gold has been for many years.
I think both notions are contradictory. An asset that is mainly "held" is highly unstable in price, because the fluid part is a small, and hence potentially very variable part of the total amount.
In Fisher's formula, this comes down to:
Q.P = M . V
with V = m1/M + 2 m2/M + 3 m3/M + ... + n mn/M
(mi = set of coins that are spent i times in a year).
If coins are mainly held, then MOST of them are in m0, which doesn't contribute to V. As such, V is a small number, but which can quickly change, if even a small part of m0 (majority in hodl state) decides to move (into m1, m2, ...).
For instance, if 95% of M is held, in m0, and only 5% is liquid, then a 5% spending from the store m0 can halve the value of a coin ; and a 2.5% extra holding will double the value of a coin.
There's some good reading on the so-called stability of the gold standard (which is what bitcoin as a world-wide currency wants to imitate):
https://www.theatlantic.com/business/archive/2012/08/why-the-gold-standard-is-the-worlds-worst-economic-idea-in-2-charts/261552/http://rationalwiki.org/wiki/Gold_standard_(economics)
http://www.nber.org/papers/w10171.pdfto give a few ideas.
Of course you can put your tin foil hat on and say that all this "research" is part of the Big Conspiration, but I don't believe that. It is genuine research.
But that is, on the assumption that bitcoin *already became* the universal money. Gold has been so for a while because *states decided so*. However, there's no path for it to *become* universal money if it has to compete with close-to-ideal money (big fiat), being a fluctuating, hoarded speculative asset.