I think the headline is very misleading though the report does kind of admit that. I saw more Peacocks here in the spring than for many years & there was a good emergence of the next brood in July. These latter butterflies usually disappear quite quickly & go into diapause earlier than many think having fed up, so I suspect when the count took place (something like a 3 week period?) many were already out of sight.
British Wildlife reported many species having a bumper year. Also the BB Count this year was restricted to a number of common, easily identified species. I would say migrant species such as Painted Lady have been few but these are due to factors beyond our shores &the numbers vary many fold from year to year.
I wouldn't worry too much about the alarmist headline.