question:  Why did Yuri go back to Cupia?
context: 6 Twelve months ago he would have been available, for he was then quietly visiting at my farm, after five earth-years spent on the planet Venus, where, by the aid of radio, he had led the Cupians to victory over their oppressors, a human-brained race of gigantic black ants. He had driven the last ant from the face of continental Poros, and had won and wed the Princess Lilla, who had borne him a son to occupy the throne of Cupia. While at my farm Cabot had rigged up a huge radio set and a matter-transmitting apparatus, with which he had (presumably) shot himself back to Poros on the night of the big October storm which had wrecked his installation. II TOO MUCH STATIC Myles Cabot had returned to the earth to study the latest developments of modern terrestrial science for the benefit of the Cupian nation. He was the regent of Cupia during the minority of his baby son, King Kew the Thirteenth. The loyal Prince Toron occupied the throne in his absence. The last of the ant-men and their ally, the renegade Cupian Prince Yuri, had presumably perished in an attempt to escape by flying through the steam-clouds which completely hem in continental Poros. 9 During his stay on my farm, Cabot had built the matter-transmitting apparatus, with which he had shot himself off into space on that October night on which he had received the message from the skies: “S O S, Lilla.” But when he had finally and fully recovered, he found himself lying on a sandy beach beside a calm and placid lake beneath a silver sky. Gone was all his languor, as he seized a piece of driftwood and prepared to defend himself. Could it be that all his adventures in Cupia had been naught but a dream; a recurring dream, in fact? The other three ants kept away from him as Doggo led him to the beached airplane, and soon they were scudding along beneath silver skies, northward as it later turned out.
output:  He wanted to rule both lands
options:  He was in love with Lilla  He wanted to rule both lands  He was afraid of Myles  He deserted New Formia