Who knows how many hours of maintenance work were required to get it functional?
It might have been just a couple.
It might have been dozens or hundreds.
Those are little more than WW2 era tanks. A tractor mechanic can get them running, and man-hours are cheap in Russia, certainly when compared to nominally 5 digit USD priced electronic parts under sanctions now that the newer tanks need for some of their fancier systems, and maintenance wise are sometimes closer to a turboprop driven aircraft than WW2 tank.
The use of T-55s as Infantry Tanks seems sensible to me. MTBs they are not.
There's a reason no one really uses those outside of specialist high mobility units that really need their tanks light. If you want to do it well, it costs as much as a MBT, see the new US not-tank.
en.wikipedia.org
It weights slightly more than a T-55, has better gun and probably somewhat better protection, and vastly superior fire control, sensors, comms and other electronics, which in turn make it cost more than a brand new T-90.
You can also use up whatever stockpiles of T-55 ammunition you have left for largely wasteful indirect fire support instead of utilizing more in demand 125mm tank ammunition for largely wasteful indirect fire support.
If their industry wasn't stretched to its limit, they could probably use the chassis to make an actual SPG out of it, even if they need to use the same, not really great for artillery work 100mm ammo, with large, SPG style turret giving the gun better elevation, more precise gun laying, specialized indirect fire control gear, and more room for loaders to work faster, which would make it into somewhat useful light SPG.