That is not profit. If an insurance business picks up 10% more clients that cost 5,000% higher expenses, they cannot just increase premiums 10%. They have to increase premiums a lot more.

Not to mention that the ACA forced insurers to subsidize old people from the young (maximum age rating factor), health to sick (can only price based on age, location, and tobacco status), and imposed out of pocket maximums. All of these mean the insurance company is spending a lot more after ACA than before ACA, and all of that had to be recouped as revenue from premiums, otherwise you have bankruptcy.

Also, all the US health insurance company financials are public. You can see their profit margin is a steady ~5% for over a decade. They are spending $95 for every $100 in premiums they take in.