2023 is a first El Niño year after a long streak of La Niña years [0]. Which means, drier-than-usual summer after multiple wetter-than-usual summers. If we assume that wetter years accumulate the fuel, and drier years burn it, it would explain a single peak in 2023 followed by lower-than-average years later.
Except that the very graph in your link shows 2023 as an unremarkable year. "El Niño after a few years of La Niña" practically happens every decade or so. Similar thing happened in 2002 and 2009: 2002 was an average fire year and 2009 was close to minimal fire.
[0] https://ggweather.com/enso/oni.htm