I'll mention the same I mentioned before in another thread:

"Correlation does not imply causation"

The fact that you have won more matches without the watching match bonus than when you have this bonus doesn't mean there's a correlation, as there are hundreds of others variations and variables involved that you are not adding to the equation (opponents' quality, own players condition and morale, tactics, win bonuses, training bonuses, individual tactics, supporters, formation, team style ...)

Watching a match gives your team a boost, but does not mean you will automatically win all games. And not watching it doesn't make your team weak and will make them start losing all games. It's just an extra bonus. Chances are that you would've lost all the matches you lost while watching them anyway, maybe by even more goals.