until M33 approached and then crossed the meridian. I noticed once my scope was facing straight up the lens became completely covered with dew. [...] Is there any reason why it dewed up so quickly?

yes. PHYSICS! heh

Seriously though, dew forms when the temperature of the air gets to be around the dew point temperature. Dew will form on your equipment when it gets to within about 3 degrees of the dew point. Our equipment cools by way of infrared radiation. If the cooling due to radiation is greater than the conductive warming from the ground (via the tripod), the telescope can cool below the dew point.

What happens when the telescope is pointing directly up is that your optics are now pointed toward space face-on. This means they are free to radiate perfectly into what is effectively a very cold sink (as opposed to a heat sink) and their temperature can fall below the dew point. When the optics are not pointed directly up, the portion facing the cold sink (space) is smaller (and is smallest when the telescope is parallel to the ground).