Still pointless to have a short rifle for artillary. Unless you are using horses to pull artillary.
Or a truck that you're constantly climbing in and out of when you're moving equipment around. And it wasn't just made for artillery units, it was for support troops in general. A shorter, handier rifle for troops that weren't expected to use them much. They still wanted the long barrels for combat infantry, for better effect at range (military thinking that was well outdated by WWII, but it's not like the Soviets were the only ones thinking this way). A short, handy, carbine length rifle was thought of as "good enough" for artillery and support troops that weren't expected to rely on them nearly as much.
Then a few funny things happened during WWII... First off, because they were so badly over-run at the beginning of the war, they discovered that
all troops needed a solid combat rifle. Second, combat infantry started picking up cast off M38's, and even trading for them, because the shorter length made them handier in the knife-fight distances that troops were predominantly fighting in, thanks to the rapidly moving lines created by mechanized warfare. Third, everyone,
every single soldier is better off if they have a bayonet option. Bullets run dry, distances close, knife fights happen. A bayo is one of those "better to have and not need, than need and not have" things. So they adapted the M38 for a bayo, and presto bango, the M44 is born and the M38 immediately ceased production.
And the M44 was a popular version of the Mosin. The Chinese, Soviets, and much of the East Block dropped the 91/30 from production (they had large stockpiles by this point) and kept on producing the M44 well into the 50s in some cases, as a good, basic bolt action that got the job done.