Can single strokes cause progressive dementia?

Sometimes. Depends on location size type and cause.
Yes. A large enough single stroke can cause dementia. The underlying disease that caused the stroke can lead to further deficits and progressive dementia.
No. A single stroke might cause behavior changes or memory problems like dementia, but the changes would not be progressive. The confusing factor is that there is often associated "small vessel disease: this means prior tiny strokes involving the central part of the brain that may have been clinically silent. This picture can be associated with a progressive dementia.
A single stroke. Is not likely to cause a progressive dementia, but a series of single strokes can.
Stroke. Depends on site, extent and cause, and type of treatment provided.