Could diabetes be the cause of cause sciatica?

No, neuropathy : Diabetes wouldnt cause sciatica, but it can cause neuropathy(nerve damage) and the symptoms can be similar. A nerve conduction study, sort of like an ekg for nerves, can differentiate between the two.

Doubt Diabetes Does: Sciatica refers to an intermittently symptomatic condition involving the sciatic nerve, a large nerve in the buttock region. Since it is derived from many nerve "roots" from the spinal cord and traverses a very long distance, it is subject to irritation in many locations. All of these can produce similar symptoms. It is unlikely diabetes is the culprit as it usually affects much smaller nerves.

Affected, not cause: Diabetics have higher rates of developing sciatica compared to the general population but diabetes shouldn't cause sciatica.

Diabetes & sciatica: There might be no relation between diabetes and sciatica. The back pain can be caused by muscle strain, spinal stenosis, ruptured disc, nerve impingement ... The treatment depends on the cause of the pain. If your pain persists, you should seek help from a pain specialist. You might benefit from a comprehensive evaluation and treatment.

No: Generally not. Although you can develop a neuropathy that can be similar to sciatica due to the diabetes. I would suggest seeing a pain/spine specialist to address your concerns.