@Mats Thanks for reaching out!
This is a great question and we're curious to know more details. What region of the country were you camping in? Was it humid as well as rainy? Did you have condensation issues on the other nights of your hike? The reviews of the Flash Air Tents are a pretty mixed bag, with some folks complaining about condensation and others saying they have no issues whatsoever. This leads us to believe that those issues are fairly situational.
As you likely know, single wall tents like the Flash Air are known for issues with condensation. The only real way to combat condensation is to create airflow through the tent, preferably drawing cooler air from down low and moving warmer air out of the top. The Flash Air tents mitigate this issue by increasing the mesh in the body of the tent, putting the vent in on the fly, and by designing the fly to stake out up off of the ground. The idea being that ample air can be drawn in from below to move moisture through the tent and out of the upper vent. Any number of issues can impact the movement of air, including hot or stagnant air, high humidity, and excess moisture, to name a few.
The best thing you can do to reduce condensation is to choose a campsite that is away from water, not in a low spot where air can settle and has a breeze, stake the tent appropriately, open the vents, and to think about where your breath is going (primary source of condensation) and allow for airflow there (not block it with the wall of the tent your pack in the vestibule, as an example).
Hopefully this helps, thanks!