My dad played for Tottenham and Wales, playing in the late fifties against Jimmy who played for Chelsea and England. They became team mates in 1961/62 season and roomed together for away games. My dad says that Jimmy is the greatest goalscorer Britain has ever seen, with Denis Law second.
Brian Clough wanted him at Derby when Spurs let him go, and wrote in his autobiography that Greaves was a great player but too modest to realize how good he was, I saw him play against my team Forest a few times , if he got the ball in or around our penalty area the home crowd went silent ,he was lethal, like in the semi final of the cup circa 1968/9 when scored from outside the penalty area with a left foot daisy cutter , him and Denis Law the best goal getters of that era .
What he was saying about it not working out at Milan holds for many English players who try their luck abroard. There is a cultural immaturity many english players have, they simply end up getting home sick.
Boozing and having a good time is probably why he didnt achieve what he could have Italians / all mainland Europeans dont know how to have fun and enjoy themselves like us English sometimes to are detriment