Earlier quoted context omitted.
A deserving; that which makes one deserving of reward or punishment; merit or demerit; good conferred, or evil inflicted, which merits an equivalent return: as, to reward or punish men according to their deserts. "Just deserts" is a common phrase that uses it in the same way.
desert i don't think means deserving. It comes from the latin desertus which means to "make barren or empty/forsake". I think in this context it means to have something fail or be abandoned at a critical moment.
https://www.merriam-webster.com/words-at-play/just-deserts-o...