When they say "let it burn" they don't mean wildly out of control like the Paradise fire. They're talking about letting it burn under optimal conditions, where

When they say "let it burn" they don't mean wildly out of control like the Paradise fire. They're talking about letting it burn under optimal conditions, where crowing and running are less likely to happen, to consume fuel that could burn sub-optimal conditions where there is little chance of control. Less fuel = less intense fire = more likely to control.