Complex sentence: In 1208, Philip of Swabia, the successful candidate for becoming the next emperor of the Holy Roman Empire, was assassinated, meaning that the imperial crown was given to his rival, Otto IV, the nephew of King John.
Split into simpler sentences: In 1208, Philip of Swabia, the successful candidate to assume the throne of the Holy Roman Empire, was assassinated. As a result, the imperial crown was given to his rival Otto IV, the nephew of King John.