What are the reasons for the weakness of the Crusader states?

As a result of the I Crusade, the following were formed: the Edessa county, the Antiochian principality, the Tripoli county, the Kingdom of Jerusalem. These states pursued their goals and pursued their policies. Although the leader in words was the king of Jerusalem, the rest of the rulers considered themselves independent from him. Often there were wars between the crusaders, during which this or that count or prince entered into an alliance with the Muslims. This also led to the gradual fall of these counties and kingdoms, since the weak and fragmented lands of the crusaders, in the end, could not resist the Muslims, who acted as a united front against them.