(Not an official answer, I'm just a regular user)<p>The ranking is a function of votes, flags, and time. Not all votes are equal, as some votes are determined to be correlated via voting-ring type considerations.<p>But if a submission gets four or five independent votes very shortly after submission then it can easily make the Front Page. It won't happen if the votes trigger the voting-ring detector, or if the submission is flagged by someone.<p>Why do you ask? Why are you surprised? What other reading have you done before asking the question?
1. They might be really new. This is how most posts go from 3-4 votes to 100+. Few people visit /newest, so posts either get a lot of points over time (less common) or briefly make the front page and "take off."<p>2. dang emails people who submitted items that were good but didn't take off and then puts them into a system that pushes them to the front page at a certain time to see if they would work once there. This has happened to me a couple of times.