A wandering albatross lays a single egg, incubates it for around eleven weeks, and then feeds the chick on the nest for roughly nine months. From laying to fledging the cycle runs beyond a calendar year, so a pair that succeeds cannot lay again the next season. Successful breeders return in alternate years; pairs that fail early may try again sooner.
The consequence is arithmetic. With at most one chick every two years, and with birds not breeding until somewhere around their tenth year, the species replaces itself very slowly. Longline fishing mortality that removes even a modest fraction of adults each year cannot be absorbed by raising output, because output is capped by the length of the cycle.
What is often got wrong is the framing of albatross pair bonds as unbreakable. Bonds are long and strongly maintained, but divorce does occur, particularly after breeding failure, and a widowed bird can re-pair. The biennial cycle, not lifelong monogamy, is the trait that constrains recovery.