Could you explain where the 40x speedup comes from, given that literally the biggest problem in semi conductors right now is smaller node size?

Just bigger chip area at lower clock could do it too if there is no threshold on cost anyway and they were limited by power. Google would hit enough accumulated production of AI chip area and cluster build out even if Moore's law stopped. There will likely be big algorithmic improvments too.

Improved parallelization. More cost in less time.

This is Nvidia's main area of research now.

Still, very marginal improvements. There is also Amdahl’s Law which limits the speed gains of parallelisation.