The Senate chose not to impeach because by the time they got around to it he was not president. It had nothing to do with the legality of it. It was even stated by several of them that the actions were now left to the justice system.
There is no reason why a president should be immune from prosecution for crimes committed during the presidency.
Its crazy how the same corporation supports shit stains like Cruz also runs Cool Zone Media that has Behind the Bastards and It could Happen here both of which are way to the left for an American audience.