Normally, the team of the yellow jersey takes the responsibility of defending the jersey, but I see a different dynamic here. Van Avermaet is unlikely to hold the lead through the mountains, but the teams of the likely GC contenders cannot count on him losing 5 minutes if they allow BMC to control the tempo.
Where's the big prize?
Though everyone was supportive of a Velogames competition without the prize pool that I've managed in recent years, Jo's immediate reaction to her elevated position was to ask, " What's the prize for leading after Stage 5?" The prize, my dear friend, is the momentary respect and admiration of your peers. Enjoy it while you can.