The Watergate investigation didn’t target Nixon personally, either — at first. That’s just where the trail led.
Will the Russiagate trail lead to Trump? If Trump is truly innocent, maybe not. But if he’s culpable in any actual collusion that may have occurred, it will be found out.
Of course, whether Trump is guilty of collusion or not, a great many of his actions and reactions are putting him in contention for the “Crybaby of the Year” award.