Step 1: Context of the man's situation.
The man, who sold rat-traps, had fallen into poverty and misfortune. He found it impossible to make a decent living from selling his rat-traps. His business was unsuccessful, and he had no other means of earning a livelihood.
Step 2: Explanation of his actions.
Due to his inability to make a living through his trade, the man resorted to begging and thievery to survive. His dire financial situation led him to take extreme measures, as he had no other options for earning money.
Step 3: Conclusion.
Thus, the man's resorting to begging and thievery was a consequence of his unsuccessful business and poverty, pushing him into a desperate situation where he had no other means of survival.
Final Answer: \[ \boxed{\text{The man, who sold rat-traps, resorted to begging and thievery because his business was unsuccessful, and he was unable to earn a living.}} \]