Monticello felt weird. You would have walked about in halls and garden walks and promenades with slaves literally hidden beneath your feet. Even the slave quarters on the hill would have been hard to spot from the mansion. Jefferson seems to have fallen in love with French fashions, and the only way to blend them into the American scene was to hide away the dark details.
If the Smithsonian article is accurate he seems to have reconciled himself to slavery sometime around 1790. Maybe it was economic considerations: you can't have the French style and enlightenment facilities without money, after all. Maybe it was personal interactions that soured him. UPDATE I forgot about Haiti and 1791. That might have reconciled a man to trying to hold on to the wolf's ears a little longer.
Given what I'd heard of him before, and noticing the prominence of Voltaire in his pantheon, I predicted that he would have engaged in some enlightened patriarchy like Voltaire's to ameliorate the lot of his slaves. Unless introducing a merit-based hierarchy with better trained slaves at the top (literally at the top of the hill too) counts, apparently he didn't.
In some ways Jefferson was an early version of Frank Lloyd Wright. He was a self taught and careful architect. But... The dome he designed was uninhabitably hot. The rainwater catchers on the promenades, thanks to ill-chosen cement, never provided usable water. He was pretty much always building with borrowed money. At least he didn't try to build a house with a living tree in the middle of it.
Some evil fruit and some excellent. A little more wisdom would have changed a lot, but that's true of us all.