Why An antenna shorter than a quarter wavelength (or half wave for a dipole) looks like a small resistance in series with capacitive reactance, so it cannot be fed efficiently. Adding a series inductor, the loading coil, supplies an equal and opposite inductive reactance that cancels the capacitive part, leaving a purely resistive feed point at the operating frequency. That is what resonance means: X_L = X_C so the net reactance is zero.
Watch out The choices about lowering Q or losses are backwards: an electrically short loaded antenna has a low radiation resistance and high stored energy, giving high Q and narrow bandwidth, and the coil's own wire resistance adds loss rather than reducing it.
Short antenna = capacitive; add inductance to cancel it. Coil cures the capacitance, but Q goes up and bandwidth goes down.