He had already earned great wealth and made a prestigious marriage before entering politics in middle age.
His extensive commercial activities in Cyprus probably explain the late start to his participation in Venetian politics.
In 1457, he was banished from Venetian territory for two years for having failed to report his brother Andrea's fraudulent election to the Zonta of the Senate.
In 1458, he purchased from Pietro Mocenigo the palace of San Cassiano on the Grand Canal, which he later made his residence.
[1] He was, however, rumoured to have assisted John's bastard son, Archbishop James of Nicosia, in fleeing Cyprus for Egypt to gain the support of the Sultan Sayf al-Din Inal for his claim to the throne.
According to a quite different rumour, he had previously worked to supplant James as archbishop in favour of his brother Andrea.
[7] According to George Bustron, James's maternal uncle, Markios, threatened to kill Cornaro and was only dissuaded by Marietta de Patras, who pointed out that the rumour was designed to sow discord.
The negotiations for the marriage had been undertaken by Andrea, but Marco helped to secure the immense dowry of 100,000 ducats.
The death of her young son, James III, in 1474 left her the de facto sovereign under the power of the Venetian provveditore.
In October 1474, Cornaro was finally permitted to go to Cyprus, where he butted heads with other Venetian officials.
In his funeral oration, Pietro Contarini praised Cornaro's honesty: "And how was [his wealth] acquired?
Not by acquisitiveness, not by fraud, not by robbery, but by ability, industry and the most honest shrewdness" (At quomodo est adeptus?