To the average person, “draining the swamp” means reducing the access and power of lobbyists, and eliminating corruption in government. To Trump, it clearly means no such thing; lobbying activity in Washington, by all accounts, has increased, and the amount of inappropriate self-dealing by Trump and his officials has reached levels never before seen in my lifetime.
So what did he mean by “draining the swamp?” In retrospect, we can see that he meant the destruction of prevailing political and ethical norms, and the firing of anyone who dares to use the law to stand in his way.