During the negotiations for his marriage, Andrea da Schivenoglia, chronicler of the Gonzaga family, described the then 36-old Count of Gorizia as "pleasant and joyful" (piaxevolo et zoioso).

The brothers had to face the hostility of Emperor Frederick III who aimed to seize their remaining "outer county" around the town of Lienz and the Puster Valley, separating the Habsburg hereditary lands of Tyrol and Carinthia, which had been possessions of the Meinhardiner dynasty until the 14th century.

The Venice Ten, who since 1434 ruled over the Domini di Terraferma in Friuli, intended to seize the adjacent "inner county" centered on the town of Gorizia itself.

During his reign his administrator Virgil von Graben was persuaded by grand promises by King Maximilian I to end his hitherto secret association with the Venetians and instead advocate the country's accession to the Habsburg Empire.

After the death of Leonhard on 12 April 1500 and the Gorizia inheritance in favor of the Habsburgs, the Venetians saw their failure solely in the actions of the lords Virgil and Lukas von Graben.

Leonhard's former deputy Virgil von Graben, who had played a vital role in the convergence to the Habsburg dynasty, took the position as a Stadtholder in Lienz from them.