"Why Wasn't This Brought Up Before Election?"

Unless you catch "hackers" in the act, it is very hard to determine who was doing the hacking. Why wasn't this brought up before election?

— Donald J. Trump (@realDonaldTrump) December 12, 2016

Homeland Security chair: I told Donald Trump that Russia was behind hacks 
-- CBS, October 26
Mike Pence Contradicts Trump, Says Russia Behind Hacks

-- Reuters, October 16

Trump Told Russia To Blame for Hacks Long Before Debate
-- NBC, October 11

U.S. government officially accuses Russia of hacking campaign to interfere with elections
-- Washington Post, October 7

U.S. Says Russia Directed Hacks to Influence Elections
-- New York Times, October 7