Both Minsky and Sharp confirmed that he resigned - then Sharp threw Nexus under the bus.
"George Sharp @GeorgeASharp
Mar 8 Yesterday, I resigned as an advisor of $IBGR. This is in no way a repudiation of the company, but just a matter of a difference in opinion. As we all know, I am all about complete transparency. I wish $IBGR luck in their endeavors"
So Sharp resigned because of the lack of transparency with Nexus.