Spoilers for stories not yet written (and spoilers if you haven't read Come Hell and High Water).
Losing River broke Quinn. Of course it did. How could it not? In the short years he had them, they changed him fundamentally. He would do anything to get them back. Anything.
So when he found them again, he made mistakes.
Not to say he didn't make mistakes for their first meeting, but he was far more patient then. He wasn't in love with River then. Not really. River was more of a curiosity at first. So he was patient. He watched and waited from a distance as River grew and changed. He waited until River was thirty years old to officially make contact for a reason.
River grew up Christian. Maybe not as strict as some Christian households but they still held some very firm beliefs. Beliefs that left no room for a Devil boyfriend. As River aged and experienced more of the world, those beliefs changed and eventually they shed most of their "Christian values" entirely. That's when Quinn saw his opportunity and started his plan to meet them and romance them.
But Quinn wasn't so patient when he next found River. They were an adult, but a very young adult. Still so sheltered and still so very Christian. They hadn't accepted their gender yet or their sexuality. They felt guilty about any "sinful" thoughts they had.
That was not the prime time for Quinn to bulldoze his way into their life and yet he couldn't stop himself. He wanted River back. By any means possible.
One thing about River is they don't handle lies well. Especially not from a romantic partner. Not when that relationship was built on a lie.
Quinn knew that from the first River he'd met, of course. He'd seen how their early romantic experiences and destroyed them emotionally because of the lies their first boyfriend told them. But he also knew he couldn't be truthful to this River and have a relationship with them.
But he couldn't lie forever. Not when he wanted his River. The nonbinary bisexual River that didn't give a fuck about Christianity. The River that helped him run Hell. The River he fell in love with and fell for him in turn.
Another thing about this young River, they didn't know about their mental health issues. They had been taught to turn to God when they struggled and He would help them. They didn't know about anxiety disorders and depression. They suppressed all that. They pushed it down as much as they could.
But when Quinn's lies came out, it all broke free. Their mental health crashed.
And they didn't survive it.
As you can imagine, this made Quinn more cautious going forward. Not to say he never made any more mistakes. In fact, being so cautious led to mistakes as well. But he vowed to never let that happen again. He would never lie like that to them again. And he would work hard to not approach them when they weren't ready for him like that again.
