Why couldn't they handle that one stormtrooper?

Question

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.)

Answer 1

The kind of trooper is actually an Incinerator Trooper/Incinerator Stormtrooper/"Burner", which are a higher and/or more lethal corp classification.

Incinerator troopers, also known as the Incinerator Stormtroopers, more simply as the Incinerators, or colloquially as the Burners were a class of stormtrooper within the Imperial Stormtrooper Corps which wielded powerful flamethrower weaponry. The troopers received intense fire combat training and were regarded as one of the most devastating of the Corps' specialized contingents, setting enemies and their fortifications ablaze with their flamethrower equipment.

Stormtroopers of this class were equipped with standard issue stormtrooper armor with red markings, a red pauldron, and a D-72w Oppressor flame projector with a backpack. Their armor had a cryaplast coat, which allowed the troopers to withstand abnormal temperatures.

Ultimately, Incinerator Troopers are not your typical Stormtrooper and going up against one of them is not the same, even though there may have been time to try in this case.

But to possibly answer some of your other quandaries, IG-11's mandate after being reprogrammed as a "nurse droid" was to PROTECT THE CHILD at all cost, and he may have determined that escaping into the sewer system was a better option/had better odds than trying to go up against this trooper without an additional escape route. What good would it be if they killed the trooper, but the trooper still burned the cantina, if they had nowhere to go? And if they would have escaped, and the Incinerator Trooper had still thrown flame, only the Incinerator troop could of followed, as opposed to other troopers who could not immediately pass through the fire...

As for Kara Dune, as you mentioned, she and the other just took on several other troopers and could in theory be quite tired, let alone a bit distressed that Din is about to die.

But also, as others mentioned in the comments by other people, this was mostly for story progression to both showcase The Child's/Grogu's abilities, but also to show his affection for Din Djarin by protecting his body in a precarious situation.