In part this is a cumulative effect. People are invited to set up a recurring donation, or include the Wikimedia Foundation in their will, so naturally there is a growing base level of steady income each year, with first-time donors on top of that.

The reason the story is coming up now is that the Wikimedia Foundation is currently "testing" the fundraising banners, in time for the big annual fundraising campaign in December. So at present, a certain percentage of Wikipedia readers in major English-speaking countries are shown the fundraising banners.

https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(WMF)#W...