I believe it was because someone asked Him who He is.
But that was not his response. Nor was it his 'teaching'. Nor was it the idealization of being "the Christ".
According to the story, Jesus was labeled and acted to fulfill the role of "the son of God". And in that culture, in that time, the son of a family-clan's patriarch was considered to be the living proxy of his father, the clan's patriarch. So much so that the word of the son was held to be equally binding as the word of the father, both within the family clan and within the community at large. So, as the "son of God" Jesus was meant to be taken to be speaking and acting as a proxy for God, Himself. NOT THAT HE WAS GOD. But that he was speaking and acting on God's behalf. He was the human embodiment of God's wisdom and will. And the stories of him performing various miracles were meant to reinforce that conferred authority.
The high priests at the time did not like this, of course, because it usurped their authority as God's human representatives among men, and they wanted it stopped. So they accused him of blasphemy; of claiming to be a god. And when they did, his enigmatic reply was, "you say that I am". Which was, of course, true.
A lot of Christians even today still don't understand this difference between being God's human proxy, and actually being God. We no longer live in a culture of patriarchal family-clans wherein the sons of the family patriarch are considered the human proxy of their father's word and will until they eventually take their rightful place as the clan patriarch.
I'm just sayin', Jesus wouldn't have said such a thing.
