Why did a branch against a window prevent condensation?
The branch block outgoing infrared radiation and reflect some of it back to the window this will keep the temperature slightly above the condensation point.
Infrared radiation is the same as heat radiation.
Most objects will block and reflect infrared radiation and this is why dew does not form under a tree or under different types of roofs and objects partially covering the ground.
The CO2 in our atmosphere has a similar effect,absorbing and re emitting the infrared radiation keeping earth warm at night,had it not been for the different greenhouse gasses the temperature changes during the day night cycles had been a lot larger.