Why is there no water then to fight the fires with?

There is plenty of water. Our dams are full. There's a good snowpack in the Sierras to replenish them in the spring.

The water cannot be pumped fast enough. The Palisades hilltop tanks were prefilled. Homeowners and firefighter are draining those huge hilltop tanks faster than pumps can refill them. Hosed water and airdrops are less effective in gale/hurricane force winds. It goes sideways. It evaporates quickly.

The landscape of the coastal range -steep canyons and hills- is tinder dry due to minimal rain and high winds. It is not forest than can 'be raked.'

We are witnessing an extraordinary situation something like the extraordinary hurricanes that have impacted the hurricane states. Preparations that normally sufficed for santa ana wind fanned wildfires are insufficient just as the the levees and pumping systems in Louisiana were inadequate to protect it's cities from Katrina.
history.com - Hurricane katrina

Trump probably knows he is lying, but also knows his cult will swallow his lies to his political advantage.