The more people infected the more mutations will occur. Mutations that delay death, make the virus lighter (more easily aerosolized), or kill a smaller percent

The more people infected the more mutations will occur. Mutations that delay death, make the virus lighter (more easily aerosolized), or kill a smaller percent of the infected (letting some people be infectious or even asymptomatic), might make the virus less deadly for individuals, but more deadly overall. All the mutations are happening simultaneously in a population. Ones that cause the virus to spread better will be conserved precisely because those viruses spread better.