Let's remember for a second that on the upper side of the wings there is lower pressure than the free stream (air far from the aircraft).
If the aircraft is travelling through humid air, the adiabatic process (which all packets of air that end up near the wing have to "suffer") dictates that:
$$P_{\infty} ^{(1-\gamma)} \cdot T_{\infty} ^\gamma = P_{wing} ^{(1-\gamma)} \cdot T_{wing} ^\gamma $$
and since we just remembered that $P_{wing} < P_{\infty}$, it means that $T_{wing} < T_{\infty}$.
Still from the wikipedia link above:
Adiabatic cooling occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand, thus causing it to do work on its surroundings. When the pressure applied on a parcel of air is reduced, the air in the parcel is allowed to expand; as the volume increases, the temperature falls as internal energy decreases.
If the initial $T_{\infty}$ was already low enough, or if there was enough umidity in the air, the packets of air above the wings finds themselves below the dew point, producing the condensation that prompted your question.
But is there a "lower" lower pressure when the angle of attack is higher and therefore making this phenomenon occur more often?
Yes, higher angles of attack mean higher lift, that is generated by higher differential pressure between upside and underside of the wing. Remember that the lift is roughly
$$L \propto \alpha \cdot V^2$$
and since the weight of the aircraft is not reduced, to keep the lift constant at lower speeds (such as the speeds just before landing) you need an higher $\alpha$.
To prevent the need of extreme angle of attacks, the effect of the flaps is to increase the $C_{l\alpha}$, meaning that for the same angle of attack you get more lift, changing the proportional relationship above.