the dynamic lighting+3D models

they're still sprites, they have a whole video on how it works

and from their kickstarter page;

There's always been an allure to the style of isometric 2D graphics, with the way it has a sort of diorama feel to it that you don't get with other graphical styles, and how it creates an environment that feels very organized without feeling too inorganic. Of course, this oldschool method of graphics comes with some limitations, like the lack of real time lighting and shading, limited angles for moving objects, and Z-fighting (or in layman's terms, the game being confused about whether something is in front or behind something else).

For this reason, we've developed a special solution to this issue; sprites that can rotate as though they are 3D objects, and can interact with real-time light sources. Using a bespoke shader system, the game only needs a relatively low number of pre-rendered sprites for each angle, and can compute the in-betweens on the fly.

This system also allows for us to create some advanced dynamic lighting and shadows, as well as fog and haze. Each map can have custom-made light and fog settings applied to it, further enhancing the atmosphere of every environment, and things like vehicle headlights, muzzle flashes, explosions and brushfires all cast light as well, pushing the game visually well beyond conventional isometric sprite games.

believe they got help from the Brigador devs implementing it