I suspect there are several variables at play. As others have mentioned, the heating, fat content and stirring probably helped the hot chocolate. Also, the chocolate probably had lethicin in it and I wonder if that also helped. I forgot to add lethicin to a batch of infused coconut oil once and it felt noticeably weaker than expected.

It's really hard to know the cause of something like this without further experimentation. It's possible for the same edible to hit very different based on when you last ate, what you ate, and how large of a meal it was. Hell, the other day I was reading about a study that found ibuprofen decreased the effects of weed. There's just so many possible reasons.