Netflix's Witcher series has been a hit in a number of ways, and that success has boosted all things Witcher. According to NPD analyst Sartori Bernbeck, Netflix's series manage to cause quite a bump in Witcher 3 game sales in Dec. 2019.
“The Witcher 3: Wild Hunt was ported to the Nintendo Switch console in October 2019, just before the Netflix series premiered. These combined factors caused the game to have a strong surge in sales during Q4 2019. U.S. December physical sales for the game were 554% higher than December 2018. [And it was] still 63% higher even when excluding the Nintendo Switch platform.”
In other words, the Switch release of Witcher 3 certainly did its fair share to lift those numbers, but the influence from Netflix's series helped sales for Witcher 3 rise in general.