When did they start keeping track of assists? 2000?
I don’t think assists even really became a valuable stat until the 10’s. I’m pretty sure nobody mentioned assist totals when the likes of Ronaldinho, Kaka, Zidane etc played in the early to mid 2000s
I believe they started in 2009/10.
whoscored.com is an excellent site for all kinds of stats and their first "assists stats" are for season 2009/10. Once I tried to find stats for the seasons before 2009, but I failed. You can find them for CL or for individual star players (probably counted by fans), but not for all the players in the best leagues.
Anyway, since they started counted assists, these are serie A best assistmen in a single season:
Only in serie A:
Alejandro Gomez 16 (2019/20)
Luis Alberto 15 (2019/20)
Ronaldinho 14 (2009/10)
Hamsik 14 (2012/13)
Luis Alberto 14 (2017/18)
Pirlo 13 (2011/12)
In Serie A+Europe
Luis Alberto 19 (2017/18)
Alejandro Gomez 18 (2019/20)
Hamsik 17 (2012/13)