Naleski was pretty highly rated after getting a bronze/gold dark horse, so if that was a good part of his rating, it might have temporarily elevated you above the promotion line. He's taken some losses since that have lowered his rating.
I've seen this before with major upsets. The algorithm should be smoothing these things out, but occasionally one person having a good game or two against an uncommon opponent who has played a lot of other opponents will shift the entire ladder up... until they keep playing at their normal level, and that shifts the entire ladder back down.
The fact that you're the only one to have gotten the gold promotion, however, tells me... maybe you deserve it? You *are* +1 through 3 games...