Well rumble IS one of the larger competitors for Applebloom'e love, being dark, mysterious, and a handsome pegasus from a strong family. So the fight occurs right before the climax, in part 3. After the climax, the story dies off terribly as the writer attempts to keep the boat afloat way past its expiry date by reliving a similar love octangle two generations later, as the grandson of snips and applebloom attempts to woo his own love interest.
...now AppleBloom too? Well, she got the paper, so is the climax about Kleenex? And if she got Rumble and Scootaloo still got Snips hanging at her flank, then what about SweetieBelle? You just can't make a shipfic about two CMCs and let the third being the third wheel of the scooter (or the fifth since Scoots scoot's got four)... Snails is beyond question, he loves DiamondTiara, because she calls him the sweetest things XD