When I said Mozilla's market share has been going downhill for most of my life, that counts the 2010-2015 market share losses. I don't think anything 2020-present retroactively caused the losses in 2010; on the other hand, I think Mozilla has been mismanaging Firefox since before 2010. I can't recall a period of more than a few years where Mozilla hasn't done some egregious mistake which alienates chunks of its user base.