We’ve already had many mutations of COVID occur in the past year. Is it crazy to think virus which infected the miners couldn’t have mutated into what we know as COVID?
Consider for example what happened in the US, in Washington state at the beginning of the pandemic. The first local community transmissions were detected weeks after they had already started happening, even though there was already a relatively high degree of alertness. Without testing, it wouldn't have been detected at all until a similar superspreading event finally took place.
The very fact that miners got sick a few years ago makes it also sound likely, based on Wuhan's history and based on the virus's characteristics, that bat-to-human transmission took place in similar circumstances as the miners' a few weeks or months before the Wuhan wet market event, had some low-key human-to-human transmission simmering in the community which people wrote off as the flu (at worse), until that one superspreading event.