What do you mean? So the fans should give up on the team, what is not the essence of supporting the club if you wont support them in easy and difficult times. My friend, Chelsea is one lucky club that i know. Even in their worst seasons I wonder how they pull things through, luckily they are in the final of the Club world Cup. They may be lucky to win PSG 
I understand your point mate, it makes no sense to be a plastic fan, a real fan would also support their club in tough and difficult times so I support that Chelsea fans should express themselves and think positive concerning the finals on Sunday, it doesn't really mean that they're bragging, other fans could picture it as that but in reality they're underdogs motivating their team and hoping they'll be victorious. Talking about luck Chelsea is the luckiest team in England, when they won their both Champions League trophies they won it as underdogs and no one could believe, maybe history could repeat itself, hopefully.