What the shazbot was the deal with the last chapter of Tales of a Fourth Grade Nothing?

I read this book in first grade. Judy Blume’s stories are generally lighthearted and comical, with some kind of low-key mischief going on in each of the first nine chapters. But then, in the tenth, we got:

• three-year-old Fudge swallowing a months-old turtle whole
• Fudge bragging as others laugh at Peter on the way to take him to the hospital
• Peter asking if he lost his pet and all the adults just being annoyed and nonchalant
• Fudge being given a party when he gets home, without the parents giving him any indication that eating a pet is wrong
• Peter’s family ignoring him at this party, then shoving a pet dog on him at the end as a surprise present

Was life just really different in the ‘60s in a way that could make any of this plot plausible? Even as a six-year-old, my disbelief ceased to suspend at this point.