They have also abandoned Steam-only and released Stellaris and Imperator on GOG.
Another interesting trend is that they made major reworks in crucial gameplay systems in almost if not all their current games, even years after release. This is what they are doing with Imperator right now, after the catastrophic initial reception. I'm not sure if this is good or bad: on one hand, they listen to feedback and react proactively to criticism; on the other, one wonders if they should have spent more time on design and beta testing in the first place.
First, the reason why they are abandoning Steam only is because they've tarnished their reputation there. Imperator: Rome was the lowest rated Paradox game at launch. Paradox cannot silence these reviews. Similar downtrends have been seen in HOI4 and Stellaris as well. So, Paradox cannot count on that cash cow anymore so they have to move onto other pastures where their name isn't as defiled by their own actions.
Second, Paradox has been treating their games as Early Access titles for a while now. They make broad-sweeping changes to their games' core systems without input from anyone but their ultra fans on the Paradox forums. Then, they face the backlash from those broad sweeping changes in their reviews on Steam. For example, Stellaris 2.0. It was the lowest reviewed patch in the history of Stellaris (still is) and cost them roughly 30% of their playerbase with those changes that, despite simplifying the game by making everything on Hyperlanes actually made the AI even more stupid. The loss of playerbase was recouped a bit by them offering the base game on almost constant massive sales for about two months after 2.0's launch. That patch completely ruined the game for me. They did a similar, but lessened thing with Imperator: Rome with 1.2's patch where they removed Mana but required gold to be the new upkeep, which taxed the economies heavily compared to 1.1 and before.