My response is the same to all doubters. Spend some time on YouTube watching interviews from 15 - 20 years ago. He was a completely different person. He had a large vocabulary. He spoke in complete, grammatically correct sentences.

His mental illness was obvious but his mental acuity was much sharper, more in the normal range than it is now.

Ask anyone who works with people who have dementia. They all say that Trump sounds just like their patients.