Automatic Weights messing up my rigging?

Hello. I am completely new to rigging, but I’ve watched a few videos and decided to start attempting to rig something myself.

I found a really nice skeleton model set on opengameart made with MagicaVoxel and I used Autodesk’s free fbx converter to change them to .fbx before bringing the model I selected into Blender for rigging. (The model looks extremely basic compared to the original, I’m assuming because of the conversion process and removing the colour palette and different lighting in Blender and such.)
I got all the bones I wanted in place, selected the mesh and then the bones, went to Object>Parent>with Automatic Weights.

Here’s where the interesting bit happens:

(Apologies for not embedding, I don’t have permission to do that apparently) :slight_smile:

I’m just wondering if this is something I’m doing incorrectly (and if there’s a fix) or if the problem lies with the model for some reason (and what I would do to remedy that).
I also apologize if this has been solved before, I searched for several different things in Google and here that it could have been under but didn’t seem to find anything relating to it.

Thank you!