Why such a sudden change? China certainly didn't change its position on the issue...
There still is no hard evidence for either the intermediate host nor the lab leak theories, intermediate host just seemed more plausible before a year was spent not proving it (and at this point the virus might have moved on).
So yes, the lab leak was largely unfounded and weaponised by racists who wanted to get their “china virus!!!” fix. Who, by the way, also kept implying that this was not accidental.
The more time that passes, the more clear it is that there is some obstructionism, and that makes the CCP look guilty.
I don't think either US political party said that no further scrutiny should be applied. Everyone wanted more investigation.
I also think that we should focus on the issue. If you want to make another issue about bias in the mainstream media, that's a much larger can of worms, and I definitely support that and agree with you.