Complex sentence: Eyewitnesses at the time were divided as to her motivation, with many believing that she had simply intended to cross the track, believing that all horses had passed; while others reported that she had attempted to pull down the King's horse.
Split into simpler sentences: Eyewitnesses at the time were divided as to her motivation, with many of the opinion that she had simply intended to cross the track, believing that all horses had passed. Others reported that she had attempted to pull down the King's horse.