I don't know enough about Bill Gates to either praise or revile him, but I do think it's unfair to condemn him for only having given away $100B so far.
I didn't find any information about the Oxford issue in that Wired article, but the Oxford–AstraZeneca COVID-19 vaccine Wikipedia page covers it pretty well:
https://en.wikipedia.org/wiki/Oxford%E2%80%93AstraZeneca_COVID-19_vaccine