In order for a friendly fire incident to happen, a number of things, generally speaking have to go wrong.

Firstly, one of the two parties (the shooter or the victim) is not where he says he is, or alternatively, one of the two parties is where he says he is, but the other guy can't read a map correctly, accidentally transposes a grid, or otherwise puts the mental 'pin' on the map not where the victim says he is. There was GPS available, but not to the level of 'you are here' arrows on a moving map such as we are used to today.

Alternatively, everyone is where they say they are, but the information does not get transmitted to the right people quickly enough. If a platoon leader radios "Crossing phase line Alpha on Route Nissan", that is a very definitive location on the map. The company commander takes that information, passes his front line trace up to the battalion commander, who then kicks it up to Division. (The US Army hadn't really converted to the current Brigade structure by 1991, so that level might be skipped.) That information then has to work its way back down to another battalion, company, platoon, and then individual tank crew. You can imagine that by the time such information has made its way all the way up and then all the way back down, the original unit is probably closer to Phase Line Bravo than the Alpha that the tank crew has reported. And if the neighbouring unit is a different division (or worse yet, corps), it gets even longer to transmit the information.

So, generally speaking, the first part of the problem is that the shooter has identified a target where, to his knowledge, there should not be a friendly. This immediately puts into his mind the default position that what he's looking at is the enemy. This is further enhanced by the simple stress that the enemy are trying to kill him, and he'd better get the first shot off. Today, we have Blue Force Tracker. All friendly units (at least at a platoon level) show up on the map on the computer monitor in front of you. Again, this did not exist in 1991.

The next part of the problem is that the target is hopefully identified as enemy before it is engaged. This is made difficult by the technological limitations. Thermal imagers are fantastic. They'll let you spot a camouflaged vehicle at a couple of miles, rapidly. The problem is that whilst they are fantastic for locating targets, especiallyt in 1991, they utterly sucked at identifying them. Video games today, or even the FLIR imagery which crosses our Facebook or TV news feeds from the current wars almost make a thermal imager seem like a black and white TV. Not so for the thermal imager on the 1980s era Abrams. At more than about 2km, the tank looks kindof like a white blob. You can locate a target at 3km in a matter of seconds. The fire control system will give you an excellent chance of a hit a few seconds after that. But good luck figuring out exactly what it is you're shooting at. Especially if there's partial obscuration by dust clouds, or if you're engaging a hull-down vehicle, or the like. Lots of long open spaces in the desert... So, absent a positive ID, your default is to look at the map, and to make sure that no friendlies are there. Which brings us back to the first problem. The other issue might simply be that the gunner is an idiot and is one step above failing the AFVID test, and mis-identifies what most of us think is a friendly as an enemy. As a result of this, M1s now have large thermal identifier panels to make it easier.

The last part of the problem is the attribution. Because of the incredible mismatch between US and Iraqi forces, and also the fact that US tanks used DU ammunition whilst the Iraqis did not, friendly fire incidents can be attributed with a much higher level of accuracy than in previous wars, where a destroyed vehicle might just be written off as destroyed by the enemy in a battle where the enemy did routinely destroy US vehicles and where the evidence, if anyone even chose to investigate thoroughly, may not be conclusive. So, having 7' friendly fire kills may not be so bad in a war. Remember, the US suffered 28 dead invading an empty island in WW2 (Kiska).