Googled it just to be sure before I posted: https://www.acvs.org/small-animal/intervertebral-disc-disease
This is one of those common breed-specific issues for Dachshunds so that’s probably why your pup developed it. As mentioned in the link, breeds with normal (i.e. not elongated) spines can also get it but it’s less common.
One of my greyhounds got this a couple years ago. It took us about a year to actually diagnose it because his symptoms evolved gradually. It started with slight difficulty on stairs so we were puzzling out whether it was an issue with pain or bad eyesight. Vets first diagnosed it as bilateral groin muscle strains, likely from slipping on the floor or ice (it was winter at the time) and doing “the splits”. So we did a few months of physical therapy, that was ineffective. Finally, he got to the point where even picking him up to carry him up the stairs caused him to scream, we took him in for an MRI he was diagnosed with this in his lower lumbar vertebra. We opted for surgery although we had no idea if it would help him or not. Fortunately, it did.
Added: What we had done was this (from the link): “Surgical decompression of the spine by removal of the bone over the spinal canal is nearly always recommended (Figure 2).”
BTW, this is neither mundane nor pointless. I hope you can get treatment for your pupper!