There is an inherently false assumption. Yes, Damascus was an important area between Egypt and Syria. However, it is the very armchair strategists you are talking about that would have planned an invasion of Damascus. It was incredibly foolish to attempt to attack Damascus, an ally of the Kingdom of Jerusalem. Aleppo was often chosen as a target and it was very close to having fallen in 1126, had Bohemund III and Joscelin concentrated their efforts instead of feuding. Aleppo too would have nipped the Zangids in the bud and Imam Zengi would never have been able to seize Aleppo and threaten the crusaders. However, they chose feuding.
Damascus was chosen because it was the land of the infidel. Any strategic considerations were downplayed by the fact that there was a considerable lobby among the new arrivals who wanted to invade it. In reality it was disastrous to invade Damascus but there was essentially nothing that Baldwin III could do to stop from pushing for the invasion since many didn't really contemplate the possibility of a Saracen-Crusader alliance. In hindsight Damascus might have important to keep the Zangids from conquering Egypt, but even then the armies of the Crusaders are far too frail to hold Damascus for long and with its fortifications damaged by whatever fighting and the besiegers almost out of supplies, the city would have fallen quickly and the Kingdom would be in a very precarious situation.