Why would Dominic Thiem switch from the pure strike 1st gen to 3rd gen, skipped widely loved 2nd gen?

So I think a lot of people knows that Thiem is now using the newest pure strike under the newest PJ. After he joins Babolat he was using...

Why would Dominic Thiem switch from the pure strike 1st gen to 3rd gen, skipped widely loved 2nd gen?