Why was the war against the Albigensians called a crusade?

The Albigensians were followers of Catharism, which was considered heretical. The Cathars were extremely influential in southern France, which caused concern among the Catholic bishops. Often, heretics were supported by wealthy townspeople, large landowners, and disaffected priests. The main defender of the Cathars was Count Raimund of Toulouse. An attempt to sort it out with the hands of the French king failed, since he did not want to quarrel with the feudal lords. As a result, the Pope announced a crusade, after which the righteous warriors will receive the lands of the heretics.