I do think it's an ego thing.
He's probably used to a more even power level with partners etc (high income, owning law firms as you said) it may have gotten boring, he might want someone who sees him as a real catch coz of his big shot job and obviously other people with big shot jobs aren't going to be seeing him as anything special or so highly successful.
When I was younger I was in a relationship with a very wealthy man, his family lived overseas and he lived her by himself.
When we got together I didn't realise there was such a huge difference in our incomes and assets.
I was on benefits and at uni at the time and I thought he had a standard job with little to no savings etc.
As I found out his family as well as himself are extremely wealthy. He always paid for everything (at first I tried to pay my way but he insisted) he used to want to go out to these really expensive restaurants and off for holidays at the drop of a hat which I honestly couldn't afford so he paid everything always, I hated that feeling.
I too at times thought - why me ? He could get anyone etc?
We were 'in a relationship for 3 years' , he told me he loved me etc all like a normal relationship, slept together spent all the time we could together etc.
But our relationship would never progress eg moving in together, engaged etc. Slowly I realised I was good enough to fuck, good enough to go to dinner etc but not good enough to commit to.
Basically for 3 years I was an unofficial escort and I was paid via dinners, movies, holidays etc.
Reflecting on it, he never loved me, I was simply a time filler and an escort so he didn't do these things alone.
I hope things for you are genuine and I'm sure you're worth so much more than you think and say.
It works for some people and turns out to be perfect.
Just set some ground rules for yourself about what is acceptable and what isn't and stand by those rules.