A species recovery program is usually built in careful stages: first understanding exactly why a species declined, then addressing that specific cause directly, whether habitat loss, a predator, or disease, before finally reintroducing or supporting the species itself, since skipping straight to reintroduction without fixing the underlying cause rarely holds for long.
Genetic diversity is a persistent concern throughout the process, since a very small remaining population risks the health problems that come with inbreeding, which is why programs often deliberately manage breeding across multiple sites or even multiple captive populations to keep the gene pool as wide as realistically possible.
Success is measured patiently, over generations rather than seasons, with a population usually needing to demonstrate it can sustain itself without ongoing intervention before a recovery program is considered genuinely complete rather than simply showing early, encouraging signs of improvement. Much of the benefit, in the end, comes from simply not giving up on it too soon.