That was a super sad episode. Masterful by Paddy Considine indeed. You could feel his pain in every movement and every word of every scene.
And sad misunderstanding in closing scene. Alicent was showing a glimmer of liking Rhaenyra again, reconciliation maybe. Then a delirious and on last breath Visery Viserys talks about the song and fire prophecy, thinking he is talking to his daughter. And Alicent mistakes the mythical hero Aegon for her son, and takes it as the permission and cue she needs to go extra hard to make him king.
So in last breath Viserys caused a misunderstanding that will gurantee the civil war.