God did not reveal exactly how and when everything would end. Daniel would not witness the end (Daniel 12:13); his task was to live his life with faith.
purified, made spotless, and refined: God would use violent and terrifying times to improve the moral and religious character of his people (compare Daniel 11:35).
Being wise means understanding God's ways and living by them. The wicked will not understand or change their ways, even if someone explains the vision to them.