Lord Mountbatten was killed by the IRA and Charles lost his confident. I think he panicked and found Diana. They barely knew each other when they married.
Yes, I think Diana said as much in interviews. Apparently she said she'd felt very sorry for him when she saw him alone at Mountbatten's funeral and before she knew what was happening, he'd lept on her. I guess they then got carried away by events and before they knew it they were married.
It's interesting to think what things might be like today if Diana was still alive. I suspect she'd be on amicable terms with Charles and perhaps remarried too, but I can't imagine she'd have liked playing second fiddle to Kate, and much less to Meghan who is far more accomplished. But I digress!