A lot of backstory on this guy and his organization: https://www.vanityfair.com/news/2022/03/the-virus-hunting-no...
TLDR is that this guy was acting as a fundraiser for research at the Wuhan Institute of Virology where they were specifically making novel coronaviruses, e.g. by creating chimeric viruses of SARS and MERS, and then using those viruses for gain of function research, e.g. by infecting humanized lung tissue in mice.