They always say it won't happen for [insert big number of years here] but it seems to happen every couple years.
They can figure those things out exactly, no uncertainty involved. They do this with the laws of physics, data taken from precise instruments and computer power. They know exactly if how and when these events will happen.
Total eclipses of the moon are common, blue moons happen around every 7 months, IIRC, super moons I don't have the percentages, but this is confluence of all three. That doesn't happen often. Was it spectacular? Hardly. To the observer it was just another TEOTM, but it was a little bigger (subtended a bigger angle). It was no biggie. I happened to wake up and take out the trash and I was aware it might be happening. Moment I stepped outside I noticed that it was quite dark out and realized the full moon was largely eclipsed (as I dumped my trash in the barrel), then saw that it was total, though off center. I think it was past its peak where I was. I had no idea what the time parameters were for this and still don't, just that it was not far from dawn.