There is an old arthouse short film called "A Horribly Slow Killer with a Very Ineffective Weapon". In the film, the killer hits his victim with a spoon. Not with all his might. Rarely. It takes him years to commit the crime.

After Inter's victory over Arsenal, for some reason I remembered this.

The comparison is quite vivid - Inter's victory over Arsenal was slow and steady, just like the killer with a spoon. Patience and perseverance can lead to unexpected results, even if the process seems ineffective at first.