The Germans were great at tactical retreat and using terrain to their advantage. Also, they got the point about the relative useful/uselessness of fixed fortifications prior to WWI. Patton was probably lucky to be relieved from 7th command after the slapping incident, because the “soft underbelly” idea from Churchill, invading Italy, was a really stupid idea, and at best, Patton might have gotten somewhat quicker — but still costly — results. I recall a propaganda poster the Germans had printed in English, and plastered around surreptitiously in Allied-held areas of Italy; it showed a big hill, anthropomorphized, picking up US servicemen and tossing them into its mouth. D-Day’s final go-ahead didn’t get done (I think I read this in Bradley’s “A Soldier’s Story”) until Stalin humiliated Churchill and ridiculed the Italian campaign, insisting the real second front be opened ASAP.
Patton likely wouldn’t have replaced Clark in Italy. Patton’s old command, under Alexander Patch, landed on southern France in mid August. I suspect Patton would have continued to lead this army, which moved farther and faster than his 3rd and reached the Rhine ahead of the 3rd.