Bullet proof vests, racing harnesses, etc, etc, all sorts of safety critical fiberous stuff like that ages out long before the fibers are degrading because the manufacturers make assumptions about the lifetime of the product in chemically harsh environments (for obvious ass covering reasons) and assign it an expiration date and users are not willing to say "well I use the product in a cool dry basement so I'm sure it's fine to go 2x the expiration" and accept the responsibility themselves so these products get replaced/recycled at a very high rate.

As others have stated, kevlar is also used in all sorts of other applications. The material can come from wherever.

Police, security and army are probably most of the demand for bulletproof vests, and the supply of used ones.

Kevlar is used for lots of things. Did they change the link to remove a statement about vests or did you read into the statement about kevlar?

"Along with the higher capacity, lithium-sulfur batteries have sustainability advantages over other lithium-ion batteries. Sulfur is much more abundant than the cobalt of lithium-ion electrodes. In addition, the aramid fibers of the battery membrane can be recycled from old bulletproof vests."

Look at the third-to-final paragraph where it explicitly mentions recycling Kevlar vests.

Not a big believer in climate change huh?