Complex sentence: All of the aforementioned cameo appearances involve him being on a bridge, as does the story of his ambush-leading to speculation that the so-called "Hornbuckle" is in actuality one of Onaga's holy men.
Split into simpler sentences: All of the aforementioned cameo appearances involve him being on a bridge, coinciding with the story of his ambush. Thus, it has become at least speculative that the so-called "Hornbuckle" may in actuality be symbolizing one of Onaga's holy men.