Low Poly Export Problem

[micheus]

I don't know anything about the Unity, but ...

Any way to get the low poly look back? Possibly, it was my fault as I might have messed up the settings.

... it doesn't looks like you have applied smooth to your model - either at design time as well as by using the exporter option (sub-D).

So, maybe you have enabled the "Export normals/smooth groups" option in the exporter option(?!) (assuming you used the Wavefront one)