Not enough men broke through the Union defenses. There was no follow-up, no support, and (most importantly) no shattered Union army.
By this time 150 years ago, the men who were going to make it back from the failed attack did. General Lee was concerned that there’d be a Union counter attack, but none came. General Meade wasn’t about to abandon his good defensive position to stumble into what might be a trap.
Lee didn’t know that of course, and he had to make preparations. He went to Maj. General Pickett and asked him to move to a defensive posture and ready his division for a possible Union offensive. Pickett famously stared at Lee with a blank look and simply said, “I have no division.”
Pickett wasn’t too far off. The attack had been a complete disaster. The units that made the charge took 50% casualties. Every field officer in Pickett’s division was a casualty. All three of his brigade commanders were lost.
Pickett himself was never the same after this, and he never forgave Lee for doing this to his troops. For his viewpoint, he was ostracized after the war by the rest of the southern generals. Calling out Lee was absolutely forbidden.
For his part, Lee took full responsibility himself. He realized that his over confidence had led to this tragedy. Under Lee’s leadership, the Confederates would lick their wounds and begin the retreat back to Virginia.