The phenomenon that we’re catching here is that search engines are working as they’re designed to — they’re supposed to surface the most fresh, recent, relevant news articles. But The New York Times or other credible, authoritative, independent sources are going to debunk a conspiracy theory like the Fort Detrick conspiracy once and they’re going to move on. And Beijing’s propaganda apparatus does not need to move on — they can churn out a vast array of content that hammers this theory over and over and over again.
The issue is that Chinese state media, which isn't really beholden to resource constraints or audience feedback, can churn out a large volume of propaganda on a conspiracy it wants to promote. The high volume of material makes it easier for Chinese publishers to take advantage of the way search works to promote fresh content.