It's Not That Bad - Until it suddenly gets worse
Human nature and wishful thinking can lead the crew to believe everything's under control. The fire truck crews may have been either overconfident in their capabilities or insufficiently assertive to the captain.
It all worked out this time; so niggling concerns might end up swept under the rug with kudos handed out to all involved.
If the fire fighters let it go a little farther or the wind is blowing the wrong direction next time, you might just wish the pax were outside the airframe instead of inside getting barbecued.