Basically, there's still a lot of room to grow. Despite AMD's Ryzen being on the market for quite some time now, the architecture's marketshare is still very low. It will take some time for AMD to head back to historical levels and repair the damage from the pre-Zen period.
Combining those statistics with the data Mercury Research has shared with us in the past, we see that AMD's rate of market share gain is accelerating, obviously propelled by strong sales during the holiday shopping season. This marks the second year in a row the company has dominated the holiday season–in 2017 the company tripled its sales on Black Friday and Cyber Monday.Source: Tom's Hardware