Men who do this are very charming and clever in how they spin things.
My ex has two (now adult) daughters with me that he doesn't see. I'm the crazy ex who trapped him. He doesn't mention the IVF that he paid for as that would slightly undermine the 'trapped' mantra somewhat.
After me he had three children with a woman who determinedly helped him get a court order for access. I mean, I had never ever once stopped him seeing the girls, but she believed him. He convinced her she was very different to everyone else by marrying her - massive proposal, massive wedding, very elaborate nursery and christening for their first born. She was pregnant with their third when she realised what a shit he was.
Next one was totally unaware he even had children. She was 5 months pregnant with twins when she found out. He had, until that point, claimed to be an only child who was NC with abusive parents. He sounded completely plausible in everything he said.
He did fuck up relatively recently. He bragged to a relatively new girlfriend a while ago he hadn't told anyone about his new job and his maintenance hadn't been recalculated as a result. She took a photo of his payslip and sent it to his two exes with younger children causing his payments, when one of them went to CMS, to almost double. He was apoplectic and showed himself up by ranting about it on his social media.
Hasn't stopped him charming people though. One of my daughters got a FB message recently from the latest girlfriend telling her that she can get in touch with him anytime and I don't have the right to stop her 🙄
I don't blame them though. If being manipulative in an amazingly charming way was an Olympic sport he'd be in with a real shout of a gold medal. Hes very very very convincing.