There was a ramp up of new WordPress and specifically WooCommerce sites starting in late summer of 2020 and spiking huge in December 2020 & January 2021. These are people that were stuck at home due to lockdown or losing their jobs and they started online businesses. The lot of those signed up for 1 or 2 year hosting plans and those came due around Feburary/March of this year. A large amount of those businesses failed, or the owners went back to work, etc etc, and no longer need their sites.
This is a plausible explanation considering that the drop in market share is not that big. It would be interesting to compare the numbers from the past two years.
