the tetrahedral structure is what is responsible for the remarkably high thermal conductivity and strength of diamond. the tetrahedral shape is the ideal arrangement of 4 neighboring atoms equally in 3 dimensions, and the carbon-carbon bonds with 4 neighboring atoms is quite strong. This also means such a highly-rigid structure is more easily able to carry atomic vibrations (called phonons), yielding a high thermal conductivity.

model is created using solidpython and openscad.
https://github.com/SolidCode/SolidPython
https://www.openscad.org/