Over year, I have helped Dr Andy Vonasch research his model on why certain conspiracies spread. He proposes that large events (such as the COVID-19 pandemic) with small official explanations (it originated from a wet market in Wuhan) are more likely to give rise to popular conspiracies. 

Two experiments provided support for his model: people were more likely to believe conspiracy theories about (invented) major events with a small official cause. This was explained by a lack of belief in the official cause. A third study looked at the most popular conspiracies on Reddit, and we observed the same pattern in these real-life conspiracies.