Some sites recover at a later update and others never do because recovery depends on genuinely addressing what the update assessed, then waiting for a re-assessment cycle. Recovery is not random, and it is not a matter of simply waiting. The sites that come back are the ones that fixed the underlying quality or pattern issue the update was weighing, so when Google re-runs its assessment at a later update, the page is re-rated on its improved state. The sites that never recover are the ones that waited without changing anything, made cosmetic changes that did not touch the real problem, or have a fundamental fit problem the site cannot resolve. Recovery requires real change matching the update’s axis plus the re-assessment that a later update brings. This is observed behavior worth verifying, not a guarantee.
The mechanism has two parts, and both are necessary. First, the change has to be real and on the right axis: if a core update down-weighted your content for thin, unhelpful, or untrustworthy material, the fix has to actually raise helpfulness and trust, not rearrange surface elements. A site that only adjusts formatting or swaps a few words has changed nothing the update cares about, so a later assessment finds the same page and rates it the same way. Second, even a genuine fix usually does not take effect immediately, because these broad re-evaluations largely apply during updates, so the improved site has to wait for the next assessment cycle to be re-rated.
That is why the split looks like luck from the outside but is not. Two sites both wait for the next update, one recovers and one does not, and the difference is whether the waiting was accompanied by real, on-axis change. The site with a fundamental fit problem (content that cannot meet the standard the update raised) may never recover, because no amount of re-assessment helps a page that still does not deserve the position.
For your next recovery effort, identify the actual axis the update assessed, make real changes that address it rather than cosmetic ones, and then wait for the re-assessment cycle a later update provides. Worth confirming against current Google guidance: how recoveries surface and whether re-evaluation timing has changed, since the specifics evolve.