Q:

Is the timing of the US-North-Korea summit in Vietnam and Michael Cohen's testimony in Congress coincidence?

Both event happened more or less at the same time. I wonder if this is a coincidence or actually a coordinated set of events? 
In particular, was the summit arranged by Trump at the same time as the hearing, perhaps to distract attention from it? Or is it perhaps the opposite, i.e. Congress timing the hearing when the summit was taking place, so as to undermine Trumps' potential success in the NK issue? 
Is there any evidence of any arrangement of this sort?  

A:

It's highly unlikely it was anything but a coincidence. While they both happened on the same day, it's important to remember that neither event can simply be executed on short notice. Consider
Congressional Testimony
Requires scheduling of

The committee members (typically a dozen or so members)
The person testifying

Cohen was originally set to testify on Feb 7 but that was postponed by Cohen, who felt threatened by Trump and his legal team. On Feb 20, Cohen accepted Feb 27 as a new date.
Diplomatic Events
Requires scheduling of

The President
The foreign entourage (in this case DPRK officials, who prefer to travel by train)
The host country

The summit was announced in Jan, and appears to have been set for the 27th on Feb 16, some 4 days before Cohen's revised date.
In order for this to not be a coincidence, you would have to believe that Cohen or Democrats wanted to do this opposite the larger story of the Summit. That makes little sense, since it would mean less coverage of Cohen's testimony, which would diminish its effectiveness in damaging Trump.

