Since this will continue to be misunderstood, it's important to emphasise that the article explicitly mentions that there is 1. No evidence to support the idea of strains that have any impact on infection 2. No evidence to support the idea that the strains will resist the vaccines or weaken vaccine efficacy. This is not a "strain" in the sense of the flu, COVID-19 hasn't fundamentally changed in any meaningful way th…
It _could_ be a neutral mutation that just spread due to a "founder affect" or something, but it would not be in any way surprising if a virus which is brand new in humans, evolved in the direction of adapting better to that new environment. What spreads better in bats, may not be the same as what spreads better in humans, and there is no particular reason to expect that this virus wouldn't be mutating in the direction that allows it to adapt to its new host.
Now, that could even be a good thing, if it was adapting in the direction of not triggering the host's immune system as strongly, since it is largely an immune system overreaction that kills the host. But, while by no means definitive, I don't think we can say that there is _no_ evidence to support the idea that strains have any impact on infection. the very fact that the initial strain has been largely displaced by others, suggests at least the possibility that it has.