Maybe? I do kinda doubt that as the original addon was benign and did exactly what it said on the tin to fix a problem one of the founders had themselves - finding and applying coupons automatically, and there isn't an obvious way or need to monetise that.
But they gained a massive userbase very quickly, which attracted investors like vultures ready to tear profits from those users. So even if they originally didn't plan to do much more than scan for coupons, after a few years of venture capital greed and tens of millions of investor money, they definitely were chasing profits by any means necessary. Money corrupts, after all.

And by the time Paypal was willing to pay $4 billion for them in 2020, it was blatantly obvious they were doing a lot of shady shit because there just isn't a way to monetise free users that well while staying above the board.

All of which is a damn shame, because the idea of an addon that scans and tries coupons for you is really simple and very useful :/

System working as intended.