The Duke of Sussex has been involved in the patronage he was speaking on behalf of since its inception using funds from a trust founded in the name of his mother way back in 2000. His father has been a climate advocate since the 1970s and is widely credited for being the one who introduced Diana to environmental concerns since the 80s... This was long, long, long before Markle was in the picture.
As for him being not “bright,” you clearly don’t know a lot about him. Maybe check out his distinguished military career, the impacts he has had on service member societal reintegration, post-conflict medical care for vets, and the loads of work he has done for mental health awareness in the private sector (again, all pre-Markle).
I get that she is a strong, intelligent woman with a lot going for her, but he is a philanthropist and advocate in his own right. He has made contributions to his country, its military, and the people who serve in it that any person would respect (especially those who claim to respect soldiers and their sacrifice and commitments).
Again, he didn’t say the virus was caused by pollution, Mother Nature, or the Easter Bunny. He said that the dramatic and temporary healing of certain aspects of the damage humans have done to the environment that came about when we all went on lockdown for six weeks highlighted how interconnected we are to the environment and how we can make a significant and humbling impact to its restoration if we so chose to do so.
Basically, he is saying to the people who use racist terms like “China virus” and use other countries negative environmental impact as an excuse to not bother doing their part to protect the environment that they need to take off their pouty pants, put on their thinking caps, and realize they can and should do their part to ensure the longevity of the planet.