All the signs, however, were there. Like previous bubbles, people were basing their belief in the cryptocurrency on their emotions, not any intrinsic value. Then there was the FOMO element, which only compounded things. Essentially, bitcoin became an international fever. Random companies were “pivoting to blockchain” for no apparent reason other than that it seemed like a way to create buzz. But when the bubble bursts, FOMO turns into fear of losing, which makes for an especially rapid plunge.
The SADF test finds the largest ADF statistic from all the windows considered. If this value exceeds a critical value, the null hypothesis can be rejected, and it is deemed the series displays explosive behaviour in at least one of the windows (taken as indication of a bubble occurring).

Cryptocurrency existed as a theoretical construct long before the first digital alternative currencies debuted.
Identifying the determinants of asset prices is one of the most important questions in finance. Traditional asset pricing theories are founded on the idea that equity prices should be determined by fundamentals such as earnings (Gordon 1959, Campbell and Shiller 1988). In contrast, the behavioral finance literature posits that prices do not always follow fundamentals due to investor sentiment trading (Shiller 1981, Baker and Wurgler 2006, Stambaugh et al. 2012). Eventually however, equity prices seem to trace their fundamentals (Pa´stor and Veronesi, 2003, 2006, Bartram and Grinblatt 2018).