I had an account with a spread betting / CFD broker in the UK about 10 years ago, and in one of their forums a user pointed out the way they work. They follow these book models:
https://match-prime.com/a-book-vs-b-book-broker-the-key-differences-between-the-two-forex-models-2/
Essentially they trade against you initially, and if you are profitable they trade with you. I don't know if you are massively profitable what would happen to your account, probably the same, they will trade with you.
At the time I closed the account I had like a 4% increase in my funds and they didn't care.
MM job looks easy.
That is an easy way to chase away a profitable trader.
That profitable trader has to change the broker continuously.

