The grip safety was added at the request of Cavalry officers.
In those days, development of new arms was assigned to the service who was the primary user of that type arm.
Rifle development was done by the Infantry Board, since the primary user of rifles was the Infantry.
They developed a new rifle, and saw that a carbine version was developed for the Cavalry and Artillery.
Since the biggest users of pistols were the Cavalry, the development of new pistols was with the Cavalry Board.
The Cavalry would develop the new pistol to suit their needs, and they would insure that the Infantry, Artillery and the Navy would be able to use the gun too.
Back in those days, the automatic pistol was very new technology, and no one really knew just how they should be set up and how they were to be used.
The Cavalry wanted an extra, automatic safety in case a trooper fumbled the pistol while managing a misbehaving horse, or while in the heat of a cavalry charge and battle.
They thought a grip safety would meet the need, and asked Browning to incorporate one in the new pistol.
There were a number of features of the early 1911 pistol that were asked for by the Cavalry Board, including the grip safety, the extra long 1911 hammer, and the very early rounded rear sight.
The long hammer and the seldom seen today, early rounded rear sight were to allow a trooper to cock the gun by shoving it down the pants leg or down the saddle.
The round rear sight quickly disappeared early on, but the grip safety remained.
To note: The Cavalry Board was composed of seasoned Cavalry officers, not bureaucrats.