How does even N2 not crack and warp the packages and boards? If I plunged my TV into liquid nitrogen I would expect it to not work - in a violent way.
There are still problems like cpu/board/components not working due to low temperature or condensation. Generally they are solved by better insulation and trying different components until you find ones that work.
Overclocking is 25% cooling and 75% picking parts that can operate at low temperatures and high frequencies.