So much evidence suggests it was not, starting with the DNC’s refusal to cooperate.
According to NBC News, Special Counsel Robert Mueller’s team recently began asking witnesses “pointed questions” about whether Donald Trump was aware that the Democratic National Committee’s emails had been stolen before that was publicly known, and whether he was involved in their “strategic release” during the presidential campaign. NBC states that the “line of questioning suggests the special counsel, who is tasked with examining whether there was collusion between the Trump campaign and Russia during the 2016 election, is looking into possible coordination between WikiLeaks and Trump associates in disseminating the emails, which U.S. intelligence officials say were stolen by Russia.”
Assuming NBC’s report is true, then it would appear that Team Mueller has put the cart before the horse. Before chasing after Trump-Russia collusion in the hacking of the DNC’s email server, they need to first establish whether a hack even happened.