Betamax, as released, was not better than VHS. It also had very low recording times of like 1 hour per tape.
Betamax was updated repeatedly, as was VHS. At no point was contemporaneous consumer Betamax able to match VHS for quality with the same recording times.
This is a persistent myth propagated primarily by people who have probably never seen Betamax in use.
Often people compare a professional version of betamax to consumer versions of VHS as well.
It was smaller, had better picture AND audio quality, and a better head to tape ratio.
It was also proprietary and stored less, which were 2 causes of it losing to VHS.
.zstd may END UP being a standard, or it may not, but sheer technical merit is not enough to guarantee it.