Nails that seem fine under polish often start flaking within days of removal. The cause is nearly always the removal process rather than the polish itself.
The nail plate is a laminate
The plate is built from many thin sheets of keratin cells bonded together, arranged in layers that give it strength across its width.
Those layers are held by lipids and by water held between them. Both the bonding material and the water content are essential to the structure.
Peeling is a delamination, meaning the layers have come apart at the free edge. It is a mechanical failure of the bond, not a deficiency of the keratin.
Solvents remove more than polish
Acetone dissolves polish efficiently, and it dissolves the lipids between nail layers with almost equal efficiency.
It also draws out water, which is why nails look chalky and white immediately after a soak and why the surrounding skin feels stripped.
A brief exposure recovers. Extended soaking, particularly the long soaks required for gel removal, removes enough to leave the edge structurally weakened.
Scraping causes the visible damage
When gel is not fully softened, the temptation is to push or scrape it off, and the tool takes the top layers of nail plate with it.
Those layers do not grow back into place. The thinner remaining plate flexes more, and flexing is what drives layers apart at the edge.
Peeling polish off by hand does the same thing more thoroughly, since the product is bonded to the surface it is being pulled away from.
Why the damage appears late
The nail plate is dead tissue, so a weakened section stays weak and travels outward at the rate the nail grows.
A damaged area created at the cuticle takes months to reach the free edge, which is when it finally becomes visible as splitting.
This delay makes the cause hard to identify, and the peeling is frequently attributed to whatever was happening at the moment it appeared.
What helps and what does not
Rehydrating with oils that penetrate the plate restores some flexibility, and cuticle oil applied regularly is the most consistently useful step available.
Hardening treatments containing crosslinking agents make the plate more rigid, which can increase splitting on nails that are already thin and brittle.
Persistent nail changes involving colour, thickness, shape or separation from the bed are worth showing to a clinician, since those can reflect conditions unrelated to manicuring.