The common cold, a Corona virus, is "successful", in Darwinian terms, because it allows its host to kill it, but only after having had enough time to be replicated and transmitted.
Let's hope Covid-19 does not become "successful" by killing off humans that are weak or excessively susceptible to it, but leaving a large enough pool in which to propogate.
This is what the common cold did, I reckon. For anecdotal proof, think of what happened in South America when the Spanish arrived. Thousands died from it, because they had no immunity at all to it.