The punch line is that game engine is too random. In the end i guess nothing matter ( your tactics, formation, value of your players). In the end it all comes to dumb luck.

My friend today won Cup finale.
He only buy the cheapest players, doesn't watch the games, he don't train his players and he don't fill morale bar of players.
But somehow he won in the finale.

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Like I said pure dumb luck of draw. If engine decided that you going to lose there is nothing you can do about it.