>>64082009 (OP)
It was a good enough turn of the century design that Imperial Russia's under-developed industry could produce at scale. It was also cheap enough to contract manufacturing from abroad in order to make up shortfalls in domestic production.
By 1917 they had enough M91s on hand that it didn't make sense to switch to something else, so they got by with a minor update.
They were working on a standard self loading rifle, up until war were declared again and just like the civil war there really wasn't time or resources to work out the kinks and get a new design into large scale production.
By the time war were un-declared because Germans were collectively breathing through their assholes, it was clear that a new weapon system was needed. This became the SKS briefly before moving onto the AK series, but they still had metric tons of M91s, M91S/30s, M48s, M44s and other nuggets on hand. Besides being usable sniper rifles until the SVD came along, there was no sense in throwing them away with the threat of WW2 Atomic Edition breaking out any second.
As such they got stored until the communism ran out and hard foreign currency was badly needed. At that point, they had already sold off all their useful military weapons to people like Viktor Bout, leaving SKSes, Mosings and Nagant Revolvers not really getting any interest. They were suitable for export as old collector guns to civilian markets but because they all showed up around the same time they saturated the market for years. That's why we saw $59 M44s being sold by the crate. The artificially low price created it's own demand, which caught up with falling supplies and the prices went up once the surplus dried up. Now a Mosins is worth about what it is, ~$400 for an old garbage rod that shoots somewhat obtainable ammunition. It doesn't make sense economically to buy one, but it isn't crazy expensive for a gun that fought in WW2, possibly also WW1 and can still be fun to shoot now (sticky bolt notwithstanding).
