He seems to have not stayed very long at his various clubs:
2014–2015 Benfica 1 (0)
2014–2015 → Valencia (loan) 10 (0)
2015–2018 Valencia 64 (2)
2017–2018 → Inter Milan (loan) 26 (1)
2018– Juventus 25 (1)
Max. 74 games at Valencia before being loaned to Inter Milan.
Does anyone know why he's moved so much?
Good question.
There seems to be a fair few fans from other teams who have been in for him in the past whom say he is over rated & his strengths are as an attacker and weaknesses are his actual defending, which doesn't fill me with confidence especially at that quoted transfer fee.
The main knock on him seems to be his consistency playing at a high level.
Plus, doing business with Juve will be an absolute nightmare, most likely similar to our dealings with Napoli in the past.
I think you're doing him a bit of a disservice.
He was at Benfica for 8 years, Valencia for 3 years, had a season loan at Inter and now is happy at Juve - it's not like they're trying to offload him.
Mendes took him to Valencia when he was young because he was a potential superstar, and he was moving all his clients there because of his partnership with the Valencia owner Peter Lim. They couldn't afford him at the time so it was a loan with guaranteed purchase.
At first he was a bit weak and more like a winger playing RB. He had a breakthrough season in 16/17 and so Mendes moved him to Inter who were getting some big backing but again and going for CL football. Again they couldn't afford to buy him straight away because of their FFP issues, so they arranged a loan.
At Inter he did incredibly well, got in the TOTY and seemed to improve a lot defensively. Juventus swooped in and stole him off Inter because of this loan to buy arrangement meant they could.
He's a very good attacking RB, has a great eye for passes and good cross, gets forward well, but that hasn't always fit with Allegri's boring defensive football and he made some mistakes defensively in the CL.
It seems like a lot of money for me, but I do think as far as attacking RB's go, there's not anyone really better, maybe Perriera at Leicester but he's often a winger, or Kimmich but he's more of a midfielder.