The game is primarily CPU bound because of all the calculations happening on screen at any given time.
All the monsters pathing around, their stats, their attacks, all that needs to be processed. Now add in the environment’s draw calls, the player’s stats/actions/movement and it starts to make sense why CPU is taking the brunt of the work.
A favorite example I’ve seen players bring up is that games like Witcher 3 run smoother on their PCs despite “looking more detailed”, but games like that have…what, 3-5 enemies on screen at any given time? It makes a big difference.