Existing Bitcoin holders spend their coins, this is the main effect of mainstream merchant adoption.
Why did these bitcoin holders buy coins in the first place? You are presuming a large demographic of people that considered bitcoins worth having when there was little merchant adoption but not worth having now that bitcoins are more widely accepted.
Besides, there's a far simpler explanation for the 2014 bear market: A correction to the 2013 bubble(s).
Exactly.
In case people didn't notice, we've been through the biggest Bitcoin bubble ever.
What goes up, must go down. The higher you go, the lower you'll fall.