The delay in airing the real Red John episode is because Jack Plotnick (Brett Partridge) is playing Red John. The Mentalist team, unaware that there would be a week delay from football anyway, agreed that there should be some extra time between Plotnick's performance as a serial killer in 2 different shows. So they crafted an alternative Red John episode, which provided numerous benefits; prevented leaks from press and allowed Heller to film the real Red John episode without such secrecy. Jack Plotnick's performance as Red John in the Mentalist is instrumental to the closing of the Red John saga, thus producers didn't want it to be dampened in any way.
The extra episode was a gift to fans, which turned into a trick. As Brett Partridge is meant to be the very last person shown in the episode, standing in front of a slide, while the sombre music suddenly turns very eerie, the episode was portrayed as the "real" episode. While it is an acute observation, for devoted fans it is a foreshadowing of the real reveal, where Partridge will be unveiled as the real Red John.
The first step to believing is thinking. This is why so many refuse to believe.
