It was a divine move in the sense that he created a surprise tsumego that crashed AG. Lee Sedol called it his 'trick move' in the post game interview I believe. Move 78 shouldn't have damaged AlphaGo's moyo if it had responded correctly. See diagram 9 here for an explanation: chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/viewer.html?pdfurl=https%3A%2F%2Fdeepmind-media.storage.googleapis.com%2Falphago%2Fpdf-files%2Fenglish%2Fls-vs-ag4%2FLS%2520vs%2520AG%2520-%2520G4%2520-%2520English.pdf&clen=4258493&chunk=true