By selling Zidane; and one could argue after we got the best from him while he was at his peak, we managed to reinvest that money very well into the team (better than most others have done with their major sales in recent history, 30M for Carroll by Liverpool, or Tottenham after the Bale sale anyone?). I mean for goodness sake in the time following the Zidane sale we immediately acquired Buffon, Nedved (who as we all know, won the ballon d'or playing for us) and Thuram, followed later by the arrival of Emerson and Ibra. You really can't beat that effort by Moggi and co; and not that it matters in hindsight, and it does come down to speculation and subjective judgement, but had Nedved not been carded in the CL semi final against Real Madrid, there is every possible likely hood that we could've taken home the Bacon that year, and our short-middle term history could've been much different (at least pre-farsopoli).
Though, I understand we could always juggle what ifs and if only's all day long, but it is a point worth considering with the Zidane sale; as we all realise Pogba is much younger, and given how Sir Alex didn't so much as give him a look in at Man U, Pogba has stated time and again his gratitude to both Juve and Conte for giving him a chance when no-one else did (now that all the vultures have come flocking in now he's proven his ability). The free transfer for Pogba in my eyes, though late in his career, might well go down as one of Ferguson's gravest strategic errors whilst at the helm of Man United.