Conversation so far:
How did Van Halen reunite with David Lee Roth?
David Lee Roth called Eddie Van Halen to discuss what tracks would be included on a planned Van Halen compilation. Shortly afterwards, Roth re-entered the studio with the band.
Did David Lee Roth re-join the band?
Van Halen's appearance fueled reunion speculation. But several weeks after the awards show, it was discovered that David Lee Roth was out of Van Halen again.

Question: Why was it only temporary?
Self-contained rewrite: Why was David Lee Roth's renion only temporary?