How to start Radovid's quest line?

I recently finished my first playthrough of the Witcher 3 and in the epilogue I got it was mentioned that
mad King Radovid has conquered all of the North including Novigrad and due to his hatred of all magic is persecuting and killing anyone related to it, including Herablists and Sorceresses.
All in all rather bleak. This really messed with the rest of my happy ending.
I can't remember having a quest related to it. I suppose it has to do with the Vernon and Ves' quest line.
Can I, and if so how, how can I avoid the rather bleak outcome?
I highly appreciate for the answer to be as spoiler-free as possible.
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How do you trigger the Radovid assassination?
You have to do a series of lengthy side quests to trigger the "Reason of State" side quest at the very end of the game. During "Reason of State" you will then automatically assassinate King Radovid as part of the quest.How do I start a favor for Radovid?
Hand over your weapons and board the ship. Follow the guard and talk to King Radovid. The King wants you to track down Philippa Eilhart, when the conversation is over make your way towards the exit of the ship. On your way a new quest will activate "Redania's Most Wanted."How do I start the reason of state quest?
How to Unlock Reason of State. This quest will be unlocked only if the player has completed the 3 side quests, An Eye for an Eye, Redania's Most Wanted, A Deadly Plot. It will start after the main quest Blindlingly Obvious if the player chose to bribe Dijkstra with information instead of fighting him.How do I start blindingly obvious quest?
You start this quest by finding Triss upstairs at The Chameleon. She will be angry at Geralt for putting Ciri in danger, and you will have a timed dialogue with 3 responses to choose from. Note: If you chose to romance her then Geralt will automatically kiss her after the explanation.The Witcher 3 , How To Set Up The Reason of State Quest , Guide
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