There doesn't have to be a "good" reason as it's just the marginal buyer and seller that sets the latest trade price.   It's not surprising that the price is rising as resolution of the scaling issue in the most favorable (for stability) possible outcome has restored confidence among traders and investors.   You could consider price action the past few weeks/months as being suppressed by the cloud over the scaling debate and that restriction is now lifted.  As for the magnitude of the swings, blockchain assets are one of the most freely and organically traded things these days.  Stocks were once like this before central banks started obsessing over them.