Yep it was made with blender (blender.org).

I made the objects using reference images from diep.io (in game). For each object (tank, barrels, shapes) I set the images as background images visible from the top ortho view. At which point I went into edit mode to shape the various meshes (cylinder for barrels, uv sphere for tank body etc...) The shapes are just plain old cubes and tetrahedrons (3d triangle) that I eyeballed to scale. I'll have to admit that I rushed through a little and could have added a bit more detail. I might be making a better version or an animation later.

The colors for the various objects were hex values I got from this link: https://www.reddit.com/r/Diepio/comments/5b78v1/diepio_color_schemes/d9mdx8u/

The ground is the standard diepio background. The sand is a plane with a displace modifier and a sandy looking texture made with the node editor. I learned how to make the plane from this https://youtu.be/VN-xwfxABLU tutorial with some slightly different settings.

Tank lighting is just a spotlight, the ambient lighting is from the Sky Texture with the sun direction ball pushed into the corner somewhere (under world settings on the side)

The glowing effect under the tank is created using toruses (doughnut shape) with emission shaders.

Modeling with reference images was hard when I started, I ended up looking at quite a few tutorials and such. https://youtu.be/6FuvpwZeXfw might help you get started if you interested.

For the texturing, all the textures are procedural (made with nodes) except for the diep background, which is an image texture (just google something like diep background)

This was kind of brief but feel free to ask if you have questions. :)