If you read the source from NASA, the decrease is due to humans using less fire to clear land for agriculture in Africa. Here is the quote:
"As populations have increased in fire-prone regions of Africa, South America, and Central Asia, grasslands and savannas have become more developed and converted into farmland. As a result, long-standing habits of burning grasslands (to clear shrubs and land for cattle or other reasons) have decreased, explained NASA Goddard Space Flight scientist Niels Andela. And instead of using fire, people increasingly use machines to clear crops.
“There are really two separate trends,” said Randerson. “Even as the global burned area number has declined because of what is happening in savannas, we are seeing a significant increase in the intensity and reach of fires in the western United States because of climate change.”"
Check your outlet better ;) don't believe their bullshit, go straight to the source for the best information.
Wildfires worldwide are on the rise, due to the climate getting warmer and dryer in many areas. As an example both Norway and Sweden is seeing record number of fires, so is Sweden. Not a massively large area was burned because we worked our butts off to stop the fires from spreading, but we have never seen amounts like this before. This is happening everywhere, so get out of here with your bs interpretations of facts.