“or is it a pivot to blame Trump for pushing it?”
I hadn’t considered that aspect. You could be on to something.
In January 2020, it looked as though Trump might easily get re-elected, with a strong economy, secure borders, low crime, and no new wars. For the media, COVID was a godsend. They could use it to cause panic among the population, implement lockdowns, and wreck the economy. Then they suppressed the lab leak theory so that Trump could not blame the Chinese government for causing the pandemic. Their strategy was successful in preventing Trump from getting re-elected.