War effects everyone. Spiegelman's wonderful recounting of the Holocaust via his Pulitzer Prize winning graphic novel are certainly a testament to that idea. As you encounter Vladek--who has his fair share of foibles--his personality quirks are all for a reason: The Holocaust.
The chapter entitled "Mouse Trap" is all about being 'imprisoned' again, despite surviving the Holocaust. And, to understand this chapter you need some background on Vladek, who is figuratively holding Mala and Artie hostage in their present world.
Vladek is amazing in that he's a survivor--both literally and figuratively--his knowledge of languages and skills as a craftsman gained him privileges and extra food while in the concentration camps. Equally, he’s capable, quick, ingenious and courageous (some would argue, even heroic), sharp-witted and pragmatic. In the previous chapters I would also argue that he's a schemer (trickster) but never at other’s expense; he never resorts to exploitation. Though Vladek had opportunities, he never deprived others of their chance to survive. Vladek lived by a strong moral code despite almost insurmountable odds. But, this behavior comes at a considerable price.
Given what Vladek, Mala and others experienced (pre and post Holocaust), Vladek's quirks should be a mere annoyance. Spiegelman's focus is on the chaotic, traumatic encounter with parental and social authority and he plays with this in all chapters because everyone was profoundly affected by the Holocaust.
As you see in Vladek, Mala and even Anja's short stay on the page, typical survivors were incapable of connecting with their children because of an unresolved grief over lost ones, survivor's guilt or flatness of affect (or emotion). Hence, Vladek does not see his son’s pain--or Mala's--only his. By the same token, he doesn't see that his behavior is 'different' and he certainly doesn't understand who/what he hurts by the choices he makes.
So really, they're all still 'trapped'. The memories of their struggle during the Holocaust have bled over into their new lives and those memories won't fade because they're too strong. Think, too, on the places Vladek and Anja hid to survive. Surrounded by rats, in a putrid garbage, a hole in the ground and fed pig slop. All of this combined to be a physical trap so the title is fitting here because it's the description of Vladek's attempt to escape a real mousetrap (the concentration camps).
The real irony, though, is the purposeful burning of Anja's diary. Art has to reconstruct the narrative, although it's a Jewish tradition to tell familial and communal history from parent to child. The transmission of stories is a means of recalling the past and forging connections with younger generations, which are the essence to community survival. So, burning Anja’s diary was Vladek's attempt to burn the memories (her words went up in smoke, like the lives to which those words would have been a testament). Spiegelman's struggle is using oral history as a testimony.