I was surprised by your post that there is many asymptomatic in elderly people in that place.
On the Diamond Princess cruise ship, the proportion of positive people with no symptoms was greater for people > 50 years than for younger people. It was about 50% or more for all age groups up to 80+.
The wet market is the obvious source, the conditions there are like a laboratory for new diseases - so it makes sense.
There has been a paper published by Chinese scientists claiming that the virus originated from a nearby lab studying bat viruses. The presence of a lab nearby is not proof, of course, but another claim is that there were no horseshoe bats for sale in the market, nor any in the wild anywhere close to Wuhan. I don't know, though, how they established there were no bats in the market (did they go around interviewing all the vendors? would you trust a vendor to admit selling bats at this point?), and even if that was the case, the virus might have jumped from a bat into some other animal sold at the market.
Anyway, it doesn't really seem to matter which scenario is the correct one.
Some depressing news, if it applies widely. A friend of mine says two friends of his have recently applied for unemployment, and are now getting regular checks. As a result of this experience, neither has any plans to return to work when that becomes possible, but want to stay on unemployment permanently.
The town of Vo, in Italy, tested all 3300 of its inhabitants on March 3, and quarantined all who tested positive. This was in addition to a general lockdown. They found 90 positives, about 3% of the town's population, more than half of which were asymptomatic. Nine days later, they tested everyone again. They found just six positives. The aggressive testing clearly stopped the spread of the virus almost entirely. The results also indicated the few new positives resulted from transmission by asymptomatics.