What changed? Mostly the party in power. At the time it was politically expedient to say that Trump was being racist or xenophobic against China, so it was deemed necessary to paint comments by him or his supporters as xenophobic conspiracy theories. Then when he states something reasonable like the lab leak hypothesis they can portray him and his supporters as conspiracy nuts. And if it could influence the election even 0.1%, that would be bonus points for some people, although I would call that a dishonest influence.
Now that he isn’t in power, they’ve decided it’s no longer necessary to avoid telling the truth.