Here's the thing, Trump fired em! to correct the problem for this or another reason. Here's the question did Trump know his Staff was colluding with Russia? could be he fired them when he found out. These fired Staff members probably had some Russian info then used that info for an edge to get onto Trumps Staff, Who Knows? And the FBI is still investigating now trying to put the pieces of the puzzle together and maybe seeking if TheDonald had anything to do with ordering Staff to talk with Putin/Russia during the election. It's all assumptions now as the FBI has not come up with a finding. You Democrats/Liberals are conjuring up scenarios for now.
LETS wait for the FBI to complete it's investigation, but its a fact the FBI stated there was no "direct" collusion between Trump and Russia in the elections. But it's evident one or some of his Staff had direct conversation with Russia during the elections.