This is just a rumor that is being exaggerated because regardless, there has been no statement from both parties. But indeed until now there have been some rumors that indeed say that Manchester United are now trying to offer Ronaldo to several clubs and maybe if Napoli really want they can join but of course this will disturb their stability I think and I don't think Ronaldo will re-enter Serie A again.
I think if Ronaldo back to Serie A especially Napoli will have no impact on the club because his prestige is not soo good as he moves to the Premier league ago. Now, he seems to try to find in new escape, but in this case, the new club is like playing a bet if want him back. So, Napoli must think back for wholeness of the club, they must know what his value is.
There may have been some increase in Sponsorship as well as some increase in sales of Jersey from this arrival but I still feel that something like this is only enough to pay Ronaldo, nothing more.
At present, if it is true that the news that Ten Hag forced the Manchester United board to sell Ronaldo, it means that it is very difficult for Ronaldo to decide where to go next because until now there is still no big club that really shows serious interest unlike Chelsea last season.