Because calling it a "naturally caused" wildfire is technically true, but only really if you don't believe global climate change causes extreme weather events.

Two sentences past what OP quoted:

> This past weekend’s extraordinary weather event, with thousands of lightning strikes, wreaked havoc and destruction on California’s forests and communities and choked our air.

Lightning storms on the magnitude seen in the Bay Area this past weekend are unheard of--which caused the many fires you may be hearing about.

One storm does not make a trend. Tropical moisture often makes its way to the California coast in late summer. AGW may increase these events, but it is irresponsible journalism to try to pin this atmospheric event, and the resulting storms, on AGW.