I think it is more because Rashford and Lingard get more attention. Usually nobody hears about Rojo because he isnt playing and doesnt do anything special on social media. The only time people talk about Rojo are those few moments he plays and makes one (or multiple) of his trademark red card fouls or the moment he picks up yet another injury. Sanchez is basically the same story. He released a movie or something but besides that he is injured and doesnt do anything on or outside the pitch. Rashford and Lingard are talked more about because they show up a lot more. Releasing a brand, wearing funny clothes and necklaces, cryptic instragram posts and in case of Lingard trying to promote his brand. All of those things happened in a relative short period too.