They are displayed in the topic_id order. The problem, I’m guessing, is that somehow the nodeBB importer is getting the data in reverse cron and is therefore creating the posts in reverse order.
You need to see that the import script sorts the posts in chronological order when it does the import. (You’ll also need to wipe the whole database and do the import again).
Good one! Looks like that should work, though if it’s not too late, I’d recommend fixing the import script and starting anew.