Why couldn't they handle that one stormtrooper?

In The Mandalorian S01E08, at around the 20:00 mark, they've pretty much taken care of all the stormtroopers.

The Mandalorian is dying and he exchanges dramatic words with Cara Dune. _{(Of course, moments later the IG-11 just has to spray some bacta infusion on him and within minutes he's completely well again.)}

There seems to be only one stormtrooper left, the one with streaks of red paint and a flamethrower. He barges into the room/house they're in and starts spraying his flamethrower. There is dramatic slowdown (plus dramatic music). Cara Dune and Greef Karga looks completely helpless. But then Baby Yoda then does his magic hand thing to reverse the flame and kill the stormtrooper.

After having easily mowed down many scores of stormtroopers not too long ago, why couldn't IG-11, Cara Dune, or Greef Karga do anything about this one stormtrooper?

(I guess one could argue that IG-11 was "busy" cutting down the grate thing, but it seems implausible that he couldn't have spared a fraction of a second to shoot down this stormtrooper, especially given all his impressive gunslinging and multitasking earlier.)