That's like throwing pennies onto a pile of gold. NVIDIA makes billions of yearly revenue. ARM makes ~300 million. NVIDIA revenue is 60% of a GPU price. ARM margins in IoT/embedded/phone chips are thin-to-non-existent. If anything, NVIDIA will need to cut GPU spending to push ARM to the moon. And the announcement already suggest that this will happen.

GPU profits should be able to cover their own R&D, especially given the obscene prices on the high end cards.

Console makers dictated that RDNA must use a forward-compatible version of the GCN ISA. While AMD might have wanted to make some changes of some ideas that turned out to be less-than-optimal, they cannot because they are stopped by the console makers paying the bills.