Like most things in life, showing up, and luck, is 50-90% of it. You may have submitted during peak traffic and simply got lost in the flood. Or you submitted at a time when the people most interested in your post happened to be awake or on lunch break.
At least in grandparent’s testimony, it sounds like the article still ended up on the front page after the second try. That’s pretty great! If articles of quality always made it to the front page on the second submission at most, we’d be living in a very good world.