He's a tragic figure, for sure. The only time he actually made a tough decision on the spot, he lost a wife and a child, and his daughter lost her mother. This alone can destroy any person. But Viserys also brought this upon himself. He saw the cheese, but not the trap in Otto's scheme. He didn't have to remarry, he could have kept Rhaenyra close to him and groom her for the role by allowing the people of Westeros to get used to her as their future queen. "Remarry to strengthen the Targaryen line", the council said. He tried to play all the angles, and now, if he chooses to follow tradition, he'll basically hand the Hightowers a clean victory over pure Targaryen blood (Rhaenyra after his decision to make her his heir). Which would make the Hightowers not just the second House in Westeros, but also bring them as close to the Targaryens as they can get. The problem is that Rhaenyra's sons aren't pure Targaryen blood. The scenes with the dragons, knowing their significance in Westeros and their connection to the Targaryen family, and which child can ride one and which can't are very important for the bigger picture. Viserys wasn't weak in the last episode. Alicent had every right to be mad, but, in the context of this power struggle, she was also pushing for a clear advantage. Something that Viserys couldn't give her. Nevertheless, Otto was happy for obvious reasons.