Right, both my personal conclusion and Krepo's own footnote was that the split push, while threatening in theory, was not in practice. TSM was rotating to him too quickly for him to do much, and TSM could have gotten far more in the trade for what CP was getting.
This was just one of those explanations where you try to find logic in an illogical situation. There is no reason for TSM to dive there, there is no reason to go for the win after establishing control of mid, there is no reason to pull out and push another lane. There is certainly no reason for Dyrus to port in under tower after the fight isn't going well.