They emptied the tanks fighting the fire.
From the article in the GP comment:
The Los Angeles Department of Water and Power in a Wednesday press conference refuted claims, including those made by Caruso, that water tanks in Pacific Palisades weren’t fully filled ahead of the fire.
Departmental officials said the three tanks in the area were filled to capacity with around 1 million gallons of water each, but those supplies were tapped out by early Wednesday morning.
“We ran out of water and the first tank about 4:45pm yesterday, we ran out of water on the second tank about 8:30pm and the third tank about 3am this morning,” said Janisse Quiñones, CEO of LADWP.What are your thoughts on that question?
I'm in Australia, while I cannot personally answer your question wrt these specific tanks I do imagine there was some means by which they were filled to the brim.
Fire tanks are generally "slow to fill* and "fast to empty" in relative terms - they form a local cache for rapid drawdown at rates much faster than "normal" water system draw.
There's also strong element in twitter and US news of petty critic for politic points .. "The hydrants are empty and there's no water" might be that kind of complaint, eg: "we emptied the tanks here holding the fire front back, the front has now moved, the tanks are now refilling" might well be the source of what became a damning meme "the hydrants are empty".
And why is there apparently no water in the fire hydrants? Something about the reservoir not being refilled appropriately?