The “coincidental” similarity of the USA 276 orbit to that of the ISS;
The launch moment “coincidentally” resulting in a very close encounter a mere month after launch;
The “coincidence” that the close encounter distance stayed just outside the ISS safety zone, with a small margin only, just enough to avoid safety issues;
The “coincidence” that the close approach happened around the approach and berthing of a US cargo ship, Dragon CRS-11.
But there is more:
When the launch of the Dragon CRS-11 was postponed for technical reasons, “coincidentally” it was decided that another US cargo ship, Cygnus OA-7, was suddenly to be unberthed from the ISS, a month ahead of the original schedule, on what would have been the original arrival date of CRS-11;
Ball Aerospace, the same company that built USA 276, “coincidentally” also built RAVEN, an instrument to monitor spacecraft approaching the ISS that was “coincidentally” attached to the outside of the ISS only a few months before the USA 276 close encounter;
As a commenter on my blog remarked, one of the US astronauts on board the ISS during the close approach, US Air Force Colonel Jack D. Fischer, “coincidentally” happens to have a military background in the space intelligence community (he served in the Space and Intelligence Capabilities Office), and his presence on the ISS was “coincidentally” bumped up to the current 51/52 ISS expedition. He originally was scheduled for the later 52/53 expedition: the change in his crew assigment was announced late November 2016.