The Russians need to capture Bakhmut because it’s a sizeable town
It’s also protecting two of Ukraine’s major command and control hubs in Kramatorsk and Slovyansk, if Russia can push through Bakhmut and take those they can justifiably claim to hold all of Donetsk oblast, which with be a huge boost for Russia domestic support for the war. Hence why Russia, and the Wagner group in particular, are throwing so many unfortunate young men at it.
That’s a huge ‘If’ of course, the Ukrainians are fully aware of this plan and have used the time the gallant defense of Bakhmut has bought to greatly reinforce both Kramatorsk and Slovyansk.
This is also pinning a huge number of Russia troops in place, which opens the possibility of a fresh Ukrainian offensive elsewhere, Ukraine has received large amounts of winter gear from the likes of Canada and Finland and there are strong indicators that the moment the group freezes hard enough to allow mass vehicle movement that we will see…. something.