IEO: They listed IEO's Which had bad reputation in the past. But the team members from the IEO's are too close to Bittrex Core Team Members. Such a bad price & all the Team members from these IEO projects dumped their bags and as a result, Bittrex lost more customers. If you check Bittrex has only a few Coins that have a volume over 100BTC.This indicates that Bittrex is falling so hard. Bittrex is the only exchange none of their IEO's were successful.
Obviously the ICO craze has declined, but it's also possible some exchanges are now no longer indifferent to wash trading. Bittrex is one of the exchanges which were supposed to do something about it, along with pump & dumps.