After hearing the symptoms that are associated with this disorder and the fact that the disorder is linked to Parkinson's disease, which Williams did suffer from, I think that it is very likely that this was a contributing factor in his decision to end his life. His family also confirmed that some of the behavior he exhibited would be consistent with the behavior of someone with this condition.
Yes, I believe Lewy body dementia contributed to Robin Williams' suicide. Dementia is a hard thing to live with, and it becomes even harder when you have camera's in your face all day every day. I am sure there was more behind it than just the dementia, but it is most likely a contributing factor.
Too often we tend to think of the mind/body relationship in simplistic, dualistic terms: the world of the mind is one thing, and that of the body is another. Yet in reality the two are inextricable, so much so that we might even argue that are not two separate entities in any sense of the word. That being the case, we cannot discount the negative effect of Robin Williams' physical health on his mental health.
I believe Robin Williams was taking medication for Parkinson's disease and that the medication, which had awful side effects, contributed to his dementia. His suicide could be contributed more-so to the medication he was taking than Lewy body dementia in terms of looking at the root cause. Symptomatically however, Lewy body dementia was responsible for his suicide.