It's not that weird. Bitcoin has a reputation for being used in the drug trade and stuff, but it's just a currency at the end of the day. People have bought plenty of legitimate items with Bitcoin, like
apartments. Some stores and restaurants are starting to accept them.
What's weirder is that he posted the listing on an anonymous marketplace. Clearly this was done for the novelty, as there's no reason to jump through the hoops of using an anonymous marketplace just to sell carrots. But hey, who cares.