In the feudal system, the Catholic Church played a huge role in the navigation of society, and the pope was considered a representative of God on earth. The kings and feudal lords thought that they were given their right to rule by God and so must always respect religion and be willing to give their life for Christianity and the protection of its followers and believers. Thus, the Crusades were viewed as a righteous holy war against non-believers, meant to defend the Christian faith and restore the holy land, and the Knights Templar fought on its front lines.
With this, it could be argued that the Templars and the Crusades reinforced the feudal system and ideology by uniting all feudal social classes of Western Europe—the rulers, the nobles, the knights, and the peasants—under the gigantic wing of Christianity and the church and their protection.
On the other hand, even though the Knights Templars' primary goal was to recover Jerusalem and other sites of religious pilgrimage and to spread Christianity, the Crusades were not successful, and consequentially the church actually lost much of its credibility after the end of the Holy Wars.
Meanwhile, religious and feudal leaders (in this case, King Philip IV of France) accused the Knights Templars of heresy and immorality—supposedly for denying Christ and worshiping other idols—and sentenced them to death on October 13th, 1307. Many Templars were hunted down, tortured into admitting heresy, and then burned alive as punishment for their alleged crimes.
With further investigation, it was decided that the Templars were actually innocent of the church’s allegations. Because of this, the church began to be seen by some as an enemy and a persecutor of the Knights Templar, and therefore a questionable servant of the Christian faith. Many began to doubt their religious leaders, and so it is arguable that, even though they were formally recognized as “Defenders of the Church,” the Templars also helped in the Catholic Church’s erosion of power.