Here is a conspiracy theory I haven't seen elsewhere, and frankly I'm a bit surprised. My theory is that fear of the pro-democracy uprising in Hong Kong caused China to release the Covid-19 virus and cover it up until relatively wide-spread. Perhaps I'm imagining causation and intention where coincidence is the operational mechanism.
For most of 2019 Hong Kong experienced public unrest and demonstrations which the CCP wasn't able to suppress effectively. Since the pandemic outbreak those expressions of discontent have largely disappeared, primarily because they were based on massed (mostly) peaceful demonstrations which are the antithesis of social distancing.
Having noted the above "coincidence," I did a web search and found a couple of commenters on reddit.com who've had the same notion, here and here. My web search, at least, turned up no widely available media sources posing this hypothesis.
I don't claim it is true, I have no insider information. I do know that China's long history teaches that holding the large and heterogeneous nation together is an almost superhuman task, rarely successful for long.
The historical norm is for regions to break off, under the leadership of locally dominant warlords. Those who would lead an undivided China are always aware of this tendency, though rarely able to resist it for more than a few decades. Clearly it is on the minds of those who have held onto power in Beijing for the past 70+ years.