No abnormal fluctuation has occured with the bitcoin from the moment Alphabay is gone until today. Back in the SR days, and on all other exit scams throughout recent history, bitcoin value plunged when markets were busted. This is not the case anymore.
At that time a significant amount of bitcoin transactions were market related, so when a big market went down, trading volume also went down. The ether flash crash was an issue of volume. If ether had the same trading volume as bitcoin, it wouldn't have craved, because one big sell order isn't going to empty the book which is what happened during the ether crash.
Now bitcoin is being used as a remittance tool, and an inflation safe store of value(or at least perceived to be), plus the massive amount of investment purchases. This has made the transaction volume generated by dnms a much smaller share of the volume.
Another factor in the early exit scam crashes was that the bitcoin investment community believed the dnms were propping up bitcoin, so speculators reacted negatively toward a big market going down.