From the NASA Goddard post:
"Though SDO sees dozens of Earth eclipses and several lunar transits each year, this is the first time ever that the two have coincided. SDO’s orbit usually gives us unobstructed views of the sun, but Earth’s revolution around the sun means that SDO’s orbit passes behind Earth twice each year, for two to three weeks at a time."
Thank goodness for the SDO. If not for that, we wouldn't only have missed out on such a cool event (since you can't see it from Earth, clearly) -- we'd also need to have someone constantly staring at the sun to be able to observe it, and that's just not a good plan.