This probably wasn't difficult. The VC' s will eventually reap a huge reward. IPO is still likely years away.y
I doubt Elon will ever IPO SpaceX. He basically hates that Tesla is publicly traded. I seriously doubt he would want to take on the headaches associated with being public with SpaceX for lots and lots of reasons.
I expect that this is an internal investor just putting a little more onto the table. I doubt it is a fresh investor unless it is someone Elon wants involved in the company for some reason.