Steemit can run bots that will automatically vote for posts based upon pageviews (and other metrics to prevent abuse). Right now that process is manual. All I can say is that the most popular steemit article (on the Internet) also made to to the highest ranking payout. Steem voter's know that viral content is quality content and good for Steem so it is almost baked in.
If something goes viral those on Steem will know it and will likely vote for you as well. The probability of you posting something that "goes viral" but doesn't get votes is very low.