Sometimes football players grow up to love a particular team and often find it hard to exit such teams and this could be situation David de Gea could have found himself in when leaving Manchester United. Right now there rumours and speculations that he could be on the verge of returning to the club he left some years back but I don't think this would be a good decision for the Spanish goalkeeper because Manchester United isn't in good shape at the moment and his presence wouldn't do much to change the status quo, so it would be best for him to consider playing elsewhere.
Manchester United did the right thing allowing David De Gea leave but did wrong signing a goalkeeper like Andrea Onana. I get it though, this was a signature wanted by Erik ten Hag during his second season with the club so as to execute and project his tactics and style of play. Disregard speculations of David returning to Manchester United, he has been offered contract extension already by Fiorentina ( 1 Yr extension ).