Archibald might be formidable, but there was little he could do alone. He didn't want to give up. He didn't have a choice for that anymore. When he decided to attack, that was it. Despite believing his cause was just, not many followed him. The ones he brought here were it. They were currently getting slaughtered. Even if he could flee, these followers couldn't. If he fled, that meant accepting that his cause was over.
He was unwilling. He thought that as long as he could end Horatio, then it would be worth it.
Hence, he tried to get to Horatio, but Horatio continued to stay out of range. Horatio cast his enhanced spells from a safe distance while the daemon, Jonathan, and Horatio's enhanced troops continued to bar his way.
As he continued to fight, he noticed that only his spot still had the fighting ongoing. He turned and saw that all his followers were gone already.
Realization dawned then.