"The reason of betrayal (historic):

Henry faithfully supported his older cousin, the Emperor Frederick I (Barbarossa), in his attempts to solidify his hold on the Imperial Crown and his repeated wars with the cities of Lombardy and the Popes, several times turning the tide of battle in Frederick's favor with his Saxon knights. During Frederick's first invasion of northern Italy, Henry took part, among the others, in the victorious sieges of Crema and Milan.

In 1172, Henry took a pilgrimage to Jerusalem (June–July), meeting with the Knights Templar and Knights Hospitaller, and spending Easter of that year in Constantinople.By December 1172, he was back in Bavaria and in 1174, he refused to aid Frederick in a renewed invasion of Lombardy because he was preoccupied with securing his own borders in the East. He did not consider these Italian adventures worth the effort, unless Barbarossa presented Henry with the Saxon imperial city Goslar: a request Barbarossa refused.

Barbarossa's expedition into Lombardy ultimately ended in failure. He bitterly resented Henry for failing to support him. Taking advantage of the hostility of other German princes to Henry, who had successfully established a powerful and contiguous state comprising Saxony, Bavaria and substantial territories in the north and east of Germany, Frederick had Henry tried in absentia for insubordination by a court of bishops and princes in 1180"