before the rifle was changed it was a common hunting rifle in 8x50R and so the peep sight. I think the orignal barrel became beyond any repair after geting the bulge near the muzzle. imho, the conversion was made between the wars when original barrels for a replacement were available without problems.
we will never know why the owner make the decision for the .22 lr conversion. just keep in mind that a gunmaker hour was not very expensive in this days. nobody whould do this with 2024 prices.

it will be no rocket science to make 5 -10 inserts to shoot 22lr on a lathe. a british enfield conversion for the little .230 morris center fire cartridge would make more work than this.