Hey thanks for your comment! I can open up the workflow a bit here. First of all, we had a team of 3 veteran jammers (one programmer, one artist and one generalist), which meant we spent the whole time working on meaningful content instead of having to learn new things or debug etc.
The main things that make this look are the low-poly models with clunky animations, crispy pixelated textures and most importantly low resolution rendering and a color reduction shader with a dithering effect. The characters are quite crudely modeled, hand-painted and animated in blender and the textures are downscaled for that pixelated look. No need to model or animate too well since the low quality just adds to the charm.
While pretty much all other art is fully created by us during the jam, the terrain and lava textures are just free online textures that we adjusted to fit the style. This meant lowering the resolution, reducing the number of colors and making the colors more vibrant and less realistic for that goofy cartoony style.
And to be honest, that's pretty much it. The main idea is just to make everything look less realistic and more crappy and low quality. You need to be consistent with it though, because any high-quality asset will easily break the immersion. The rest is just about general eye for design, lighting and composition really.
I hope this explanation helps!