That may be because the job ran out of memory, but the size of what you're trying to import isn't at the level where we usually see problems starting to happen. From that error message I will guess you were running on a worker that got blocked partway through the job: try it again and it should just fill in what it doesn't have yet. If the second attempt this morning doesn't work, let me know, I'll put you on the list of Jobs We Have To Run In The Special "Watch Everything It's Doing Like A Hawk" Mode and we can dig into it further.

(It will say that you have to import entries again to import comments, but that's just to make sure no new entries have been posted: it won't run through the whole slew of entries again, just check on whether there's anything new.)