Betamax was a proprietary standard that largely was controlled by Sony even though they licensed it out for others to make some VCRs. NACS instead is provided license free and is now controlled by SAE under J3400.
Tesla makes up almost 60% of the DC charging stalls in the US. Even if Tesla installs zero new stalls going forward (which clearly is not the case given recent reports some were just installed), it's still a huge advantage to have supercharger access.
Tesla Accounts for 58% of All New US DC Fast Charger Ports Added in 2023 Through May – EVStatistics
Also, although the timing is bad, Ford and Rivian already have access to the network and GM is in testing phases. So right now the biggest players already have access or are in the process of having access. Any EV that decides to abandon NACS and give up supercharger access would have a huge disadvantage, as they lose access to well more than half of the DC charging stalls in the US. I personally would never consider an EV that doesn't have supercharge access, I'm sure a lot of upcoming EV owners are the same (given the initial buyer group that are less concerned about charging has been well saturated already).
The rumormill had some German makes reconsider in their boardroom meetings, but those were iffy in the first place, given lack of 800V support thus far. I think they will thumb their nose and continue on because the cons of not doing so greatly outweighs the pros.