This woman is just 'The One' for now. 'The One' who feeds his ego at this moment, but there will be another 'One' along soon enough.
My STBXH found 'The One' in January and had practically moved in with her a couple of weeks later. I'm sure he was cheating on OW2 with 'The One'. Introduced my kids immediately to her - she must be special lol
But really she could have been ANYONE. Same in your situation, anyone who came along and stroked their egos. He's broken and delusional and she'll see through it soon enough.
Try not to look anymore. It's hurtful and he is so not worth your time and internet usage