I'm sure it's been said upthread, possibly by me, but a coincidence is defined by how remarkable we think it is that 2 or more events occurred and appear, in our minds, to be linked.
If we are aware of 10 events, there are 362,880 potential "pairs". We notice the 1 "coincidence" but we do not notice the 362,879 that are, to us, unremarkable. Someone else, with a different life experience, or different priorities, might notice a different "coincidence".
Of course, in real life, we are all aware of far more than 10 events, every day. I've lived over 22,000 days, so it would be surprising if I had never experienced a remarkable coincidence.
It's like the "coincidence" that the planet we live on has exactly the right temperature range, minerals, water, comfortable gravity, etc. for us to be able to live on it. Apart from the fact that we could live on it if any of the key variables was very slightly different, the main point is that if Earth was not suitable for life, we wouldn't be here on Earth to notice how remarkable it was. There is no one on all those barren planets bemoaning their bad luck that their planet is not suitable for life.
Coincidences are engaging and fun, but they exist only in the eye of the beholder.