Does a buyer have any obligation to explain why they walked away from my asking price?

No, generally not — outside of specific commitments in a signed agreement, such as a letter of intent's own terms, a buyer is typically free to walk away from a negotiation at any point without owing you an explanation, and many simply don't provide one, whether out of their own negotiating strategy, discomfort, or simply moving on to another opportunity.

The nuance is that a lack of explanation doesn't mean there's nothing to learn from the experience. Buyers who do offer some feedback, even informally through a broker, can give you genuinely useful information about how your business, your financials, or your price were perceived, and it's worth asking, even if you don't expect a full or honest answer, since sometimes you'll get more than you assumed you would.

If a buyer walks away without explanation, it's worth reviewing the process yourself, ideally with your business lawyer or broker, for anything that might have contributed, rather than assuming it was purely about your price, since the same underlying issue could come up again with the next serious buyer.