I find it highly unlikely they will find anyone willing to pay $2 billion American for an NBA franchise. Revenues in many markets are likely to have decreased from previous highs for a few years even after the COVID vaccination has been given to the majority of the population. There is too much economic uncertainty in the near-medium term for any potential owner to pay this much money for a franchise is any place other than a large market.
You would have to give me the date on the picture. As it stands during the Canucks recent horrid run the team still averaged 96 - 98% capacity over 6 years so they in fact were selling nearly all their seats during the tough times. And no, contrary to your claims, you do not have to sell out every hockey game during the tough times to prove you can support the NBA (sellouts during the tough times according to you). Almost every team in the NBA does not come close to sellouts during the tough times especially if those tough times extend beyond more than one season. It's not a reasonable ask on your part.
Nor is basketball a niche sport in Canada as you claim. It's not the 90s anymore. No country in the world provides the NBA with as much talent as Canada. Immigration brings in hundreds of thousands . More than one in five immigrants have been born outside Canada, 13.4 % of recent immigrants were born in Africa and half the foreign-born population is from Asia - many of these people come from countries that love basketball and will provide a pool of future players and ticket buyers.
The Daily — Immigration and ethnocultural diversity: Key results from the 2016 Census
Vancouver was given a whopping 6 years in the NBA which is pathetic and far less time than any recent NHL franchise, including Atlanta. Half a decade is hardly adequate in determining whether a city can support a pro team. Vancouver was also hamstrung by terrible draft rules at the time. This wouldn't be the case if a team relocated/expanded to Vancouver. Southern BC has nearly 1 million more people, has a highly diverse population with many originating from basketball-loving countries, and the huge tv contract provides unprecedented financial stability for all NBA teams including sad sacks like Memphis, Minnesota, New Orleans.