Theory? Isn't that even an expected result? The virus started in the exact city where one of the top labs in the world. This was either a breach of higienisation protocols or intentional. Of course, claiming it was intentional is a conspiracy theory and likely won't be able to be proven ( even less likely as some doctors were knowingly suicided ).
China ended 2019 in a huge crisis and 2020 as the number one world economy. Quite a dramatic change for a year, no?