Nvidia had boatloads of money to spend, and 6X the number of engineers. AMD was skating on the edge of bankruptcy. AMD bet the farm on Zen, and that bet paid off so now they have money to spend on other things.
If they would have split resources off of Zen to spend on CUDA they would have failed at both and AMD would be a bankrupt husk.
If they would have split resources off of Zen to spend on CUDA they would have failed at both and AMD would be a bankrupt husk.