I played Acquisitions Expert in MTG Arena. My opponent reacted with Stomp adventure of Bonecrusher Giant and killed the Acquisitions Expert. Even though I saw my Acquisitions Expert's ability still being on the stack after Stomp resolved, Acquisitions Expert's ability did not resolve and opponent did not have to discard a card. Why did this happen? I just can't figure it out.
It should have resolved. But a crucial part of that would be knowing how many creatures were in your party when it resolved. If the Acquisitions Expert was the only one and was dead when the ability resolved, the ability won't do anything useful (reveal 0 cards and discard 1 out of 0 cards means discard nothing).
The Expert makes your opponent reveal cards equal to the amount of creatures in your party, you then choose one of the revealed cards to discard. What often happens when you play the expert on turn 2, is that you have no other creatures in your party.
What then happens is if your opponent is savvy is that he kills the expert in response to its trigger. This leaves your party empty when the ability resolves, meaning you reveal 0 cards and making it impossible to choose a card to discard.