Linda,
Jeff Kern led GCM after Tom Schroeder. Tom came out of the Ohio State vein of GCM and Jeff came out of Michigan. My understanding is that Jeff had convictions to partner GCM with other organizations and realized that GCM did not exist in a bubble. He began relationships with groups like Campus Crusade and Dr. Luder Whitlock from Reformed Seminary. Jeff began introducing theological training into the staff structure and saw it as a need for missionaries. That created tensions within the overall structure as Jeff was moving towards more of a reformed structure within GC and the tensions could be felt at national conferences and, from my understanding, national leadership conferences. There was a power struggle of sorts as to who would be the banner carrier for the organization, Great Commission Churches (GCC) or Great Commission Ministries. That is when Faithwalkers began. It was a statement against the direction Jeff was trying to move in. You still see some of the ramifications of that today as Reliant has distanced themselves from GCC. They still serve as a sending ministry, but they also serve many other organizations and not GCC exclusively.
To answer your question, I believe Jeff committed the unpardonable sin (in their eyes, not mine) of interviewing for a leadership position with another organization. This sent alarms off throughout the "committed" of the movement and he was asked to resign because he was not seen to be fully loyal. My understanding (from an inside source) is that he did not wish to do so and that certain people jumped on the opportunity to remove him. I have the UTMOST respect for Jeff; not per se as a perfect man who never made mistakes, but because of his big picture vision to move the movement towards more gospel-centered teachings. I was always encouraged and refreshed by his commitment to partner with others outside of GCx for the gospel. I do hope he is doing well. My understanding of his successor, Tom Mauriello, is that he is also a man who casts a larger net and sees Reliant as just one part of something greater that God is doing.
Moral of the story, "If you want to rid yourself of someone, question their loyalty to the organization (and therefore Christ)."
FALSE INFO here - Jeff Kern had suffered major health issues. Do not post information that is assuming or untrue. That is about 85% of this webpage.