IMO Pontiac would have been the perfect brand to evolve into the EV space.
Pontiac had no brand equity at the time due to many years of mismanagement and it was unknown outside North America. I can't imagine that any other company would have paid much for it.
And GM never sold the hummer brand, they still own it. Hence the hummer EV.
Considering Ford used to ship vans to the US with passenger seats, then unbolt the seats and send them back, for tax benefits, saying "we bolted a Buick logo on the ones going to China and a Pontiac one for domestic markets" is trifling in comparison.
I wonder if they'll eventually reinvent Saturn as an EV brand. Hummer has specific connotations, and those don't mesh with a consumer saying "I'm cross-shopping the Model 3, the Ioniq 6, and the Prius Prime". I figure of their classic brands, Saturn is the one that screamed "I'm innovative and a bit different from traditional GM".
It's a historical accident. Buicks were the car of choice for party members and government officials in the postwar reconstruction boom so it became the prestigious brand when GM entered the Chinese market in the 1990s via a joint venture with SAIC.