Mesut and others Real Madrid players

The ex Real Madrid player, who is one of my favorite football players in the world along with other Germans is being now rejected by his own German fans right now. I don't understand that. Mesut is not a great promise anymore, he is an experimented player and of course he can not play like he did when he was 21. It is true that maybe he is not giving us right now the top of him during the last two games in the World Cup but I can tolerate German fans when they boo to their player that way rather than support him. I wish that kind of attitude would be fixed someday by fans, not only with Mesut Ozil but with every player, is disgusting.