The meeting between Trump and Kim is just for show the important 'discussions' have been taking place between the offsiders and positions have laid on the table. The US now knows their demands are not going to be met, Kim will not give up his nukes and any talk of disarmament will not be entered into till after a peace agreement is signed between the north and south.The discussions between the United States and North Korea are ongoing and have moved more quickly than expected," the White House said in a statement.
This allows them both to go into the 'historic meeting' knowing exactly the stance of the other and that whatever they say to each other is unlikely to change things. They can then smile talk pleasantly and at the end shake hands as if they have actually done something. Unless Trump throws a wobbly as per his recent attack on the Canadian PM.