Why does increasing resistance make a capacitive sensor more sensitive?
A capacitor is created from two conductors with a dielectric between them. The capacitance of the capacitor is determined by the surface area of the conductors and the distance between them. The larger the conductive surface, the higher the capacitance. The further apart the conductors, the smaller the capacitance. Using a higher resistance means that you can use a smaller capacitance, i.e. be further away from the sensor, to get the same results.