Chapter 9: The Marshal - S2-E1
Stupidity: In Cobb Vanth's flashback, the miners are watching the Death Star blow up (evidently the Rebellion had a camera crew there to capture the moment, or they bought a neat home video version of Return of the Jedi) but the evil mining syndicate enters the bar and guns down everyone. So they are killing the...harmless and weapon-less miners they want to force to work for them? The town is minuscule, they may have killed their WHOLE workforce there. (00:20:35)
Chapter 9: The Marshal - S2-E1
Stupidity: Mos Pelgo has been around for decades, but nobody has ever thought before of the stratagem used at the end of the episode, which didn't need the Mandalorian or anything more than what the villagers already possessed (being a mining town they had a lot of explosives just lying around).
Chapter 9: The Marshal - S2-E1
Stupidity: The bad guys have guns literally at the neck of Mando, but when his slow and erratic homing projectiles fly around, they don't shoot. Slowest reaction times ever.
Suggested correction: They may not have known what the projectiles were. Some kind of weapon would be the obvious assumption, but by the time they likely figured that, they were either panicking or simply not focused on shooting Mando, since doing so probably wouldn't save them.
Chapter 9: The Marshal - S2-E1
Stupidity: Mando needs to find the settlement. Asks for information and goes there by...speeder bike that he borrows from Amy Sedaris. Why, it is unexplained. He could more easily spot the settlement from the sky, cover greater distance, and be safe from threats.