Why did Philip fight Franz von Sickingen in 1523?

Philip of Hesse fought Franz von Sickingen in 1523 because Sickingen had initiated a rebellion in 1522 to defend the class interests of the Reichsritterschaft (free imperial knights).12

As part of this uprising, Sickingen declared war against his long-standing rival, Richard of Greiffenklau, the archbishop of Trier. Philip, alongside the electors of the Palatinate and Trier, rallied to support the archbishop against Sickingen’s forces. The defeat of the rebellious knight not only repulsed his attack on Trier but also served to crush remaining opposition from the Hessian nobility, significantly bolstering Philip’s own political authority and self-confidence.21