I feel guilt over my sister's assault

I don't really know how to process this, and I'm hoping people here might understand the guilt I'm feeling.

A friend of mine had been around my house before. He'd seen my sister at parties and when he was visiting and I'd always thought he was a genuinely decent guy. We were good friends and I trusted him.

One day he told me he had a crush on my sister. I wasn't angry at all. Because I trusted him I properly introduced them when he was at my house.

After he left I asked my sister if she'd consider going on a date with him. She said maybe, so I told him to ask her and see what she said. I genuinely thought I was doing something harmless. I thought he liked her and that he was a good person.

They went on a date.

About a month later he leaked intimate images of my sister around school. That's when she told me that he had sexually assaulted her. The police became involved after that.

I'm struggling enormously with the fact that I introduced them.

I keep thinking that if I hadn't introduced them, maybe none of this would have happened. If I hadn't encouraged him to ask her out maybe she wouldn't have gone on that date. I trusted him and my sister trusted me enough to be around someone I'd said was okay.