Why did Picket's Charge fail at Gettysburg?

13,000 men lined up in a neat formation(s) crossing a full mile (open field) under union artillery was likely doomed to failure. Then at the end, 2,000 Union infantry entrenched behind a stone wall, firing point blank into the few survivors.

Kudo's to GA Custer & his Michigan cavalry who stopped Jeb Stuart's cavalry, trying to attack the union line from the rear.

Southern general Longstreet knew this attack would fail. But he couldn't talk Lee out of it.

1) J.E.B. Stuart's sweeping flanking maneuver was thwarted by George Armstrong Custer.

2) The attack on Culps' Hill (which was to draw the union forces into artillery range) was generally ignored and forces were sent to reinforce the Union's center.

3) The artillery bombardment (meant to decimate the Union forces) failed.

4) Picket's men had to cross three-quarters of a mile of open field.

1. The artillery that was supposed to soften the Union lines was ineffective.

2. Stuart was supposed to attack the Union lines from behind but he was cut off by Union Calvary.

3. Thanks to advancement in rifle technology, frontal assaults had become mostly tactically obsolete, something that was proven over and over again during the war.

I watched a documentary (Battlefield Detectives?) a few years ago that argued that a wooden fence had slowed down the Confederates.