1. Should it be surprising that trading is lower on a holiday?
It shouldn't. It's pretty obvious that traders, whales, etc, are taking some time off from the market during the holidays, they probably left some bots to excute their trades while they spend some quality time away from the crypto space.
What should we do now? Stay on the market and keep monitoring the market behaviors or take off too?
There's nothing major going right now, just some usual fluctuation, imo things will keep going sideways even after the end of the year so I wouldn't change my plans for the short-term if I were you. However, I do recommend taking some time off and stop looking at the charts so often, we're in the holidays season, enjoy yourself and stop worrying about the market movements (: