Juve finished seventh two times in a row before Conte took over. They won the scudetto right away in his first season and won it all of his three seasons there. Juventus has since won the scudetto every year until Conte won it with Inter this year. Conte took charge in Chelsea when they had finished 10th the previous season. Again, they were able to win the league right away. Second season they were fifth and first season after Conte left, they were third. Mourinho is known to leave ruins behind him but Conte actually leaves competitive teams behind him. This is of course great if he is not expected to stay long in Tottenham.
He has won the league five times during his last seven seasons and none of the teams were even close to winning the league before he took over. He really is a magician. Only Spurs can ruin him.