High Frequency Excitation on Class D Amplifier
I suspect your FET failure was from cross conduction ( aka shoot-thru) and lack of dead-band which created heavy current spikes and that triggered induction ringing in faulty probe measurement method giving the illusion of overvoltage.


If your probe ground lead is 100 mm long then it will be about 100nH and the coaxial 10:1 probe capacitance of 75'ish pF/m resonates in the 20MHz region. So keep gnd connection &lt; 1cm without clips ground wire using tip and barrel. then the true flat BW of the impedance-matched probe can occur. ( search here or web for Tek probe spring)

Now at 80V your parasitic trace inductance and capacitance adds another resonance that must be dampened with a series R due to mismatched impedance load to low Rds, high Coss switch when drain coil is switched off.  

What is the deadtime in your C-MOSFET bridge? It is this time when stray reactance resonates and minimizing Q is critical for ringing. Often Ferrite sleeves or SMD beads are used to absorb ringing but inherent shunt resistance of lossy beads. Consider impedance matching methods.  Low inductance grounding is also critical using braid or Litz wire or low L/W ratio tracks and also high self resonant frequency L.

So generally slowing down high side turn on with a matched Series R to gate resistance and using a low ESR diode to turn off such that T=R*Ciss is slower turning on than off creates dead-time of 0.5us or more may fix shoot thru, but this timing is affected by Vgs,  V+ and junction temp.