If Pickett had received the cavalry support he was promised the attack would have been a success. Instead Lee’s (Stuart) cavalry was totally out of position off on a goose chase after Meade’s (Custer) cavalry.
Where was Pickett promised cavalry support in is assault on Cemetery Ridge. Lee makes absolutely no mention of cavalry support for the assault on Cemetery ridge in his after action report to President Davis. In that report he praises Stuart for his defense of the left flank of the army on the second and third days of operations at Gettysburg.