I understand that when there is inhomogeneous broadening in a laser cavity, the resultant gain profile is a Gaussian (as opposed to a Lorentzian profile for homogeneous broadening). Due to the wider nature of a Gaussian profile, it is natural that multiple modes fall within the gain bandwidth (FWHM/full width half maximum). This subsequently leads to the possibility of multimode oscillation.
However, I am struggling to understand why exactly this leads to multimode oscillation. Why can't there be multiple modes within the bandwidth, with only one of them oscillating?
To summarise the question: how does this specific broadening mechanism lead to multimode oscillation?