Well, ok so it has only tanked on a few exchanges while picking up volume on certain others. Let's take a quick look at this phenomena.
Here is the Bittrex BTC/USDT weekly chart showing diminished trading volume

Where is everybody? This is the weekly for BTC/USDT with the volume highlighted. What does this mean?
It would be mostly speculation on my part so I'll just say, it doesn't seem like a good thing. Perhaps it is just because of all the other options available in comparison to 2018.
Interestingly, we are pretty much at the 50% FIB for the whole run up starting back in 2015 as well as the 50% FIB from the low at the beginning of 2019.
So that's just Bittrex right? Well, kinda. Let's look at Poloniex...
Here is the Poloniex BTC/USDT weekly chart showing diminished trading volume, and the recent pickup

Equally as bizarre as the Bittrex chart if you ask me even though here we can see the volume has picked up since December 2019. The pick up in volume is seen along with the low price we have seen since the same time. The last pick up in volume at the end of 2018 also corresponds with the low price/ sell off.
So Poloniex has diverged from the extreme low volume that Bittrex has remained in. But now let's look at a few exchanges where the volume has done the exact opposite, being relatively low during the same time period as Bittrex and Poloniex volume were staggering and are currently experiencing strong trading volume...
Here is the Huobi BTC/USDT weekly chart showing rising trading volume

Take note of the steady pickup in trading volume without any sign of slow down of the same time period. BTC/USDT trading pair is very active and has been steadily rising.
Along with HitBTC who has the most dramatic increase in volume...
Here is the HitBTC Bitcoin/USDT weekly chart showing extreme rise in trading volume

I took notice of these volume differences while checking out the Bittrex trading pair. I don't see heavy volume coming back to the pair on Bittrex because of several reasons while the number one reason being there are other USD stable coins trading including the BTC/USDfiat trading now available. In other word's, there are other options. I won't get into ideas of why certain exchanges are high volume while others low other than that. Anything criminal or conspiratorial that might be taking place is not something I want to investigate, even if this anomaly makes it seem like it could be worth investigating for the crypto community as a whole.
It's worth noting.