I am very sorry to hear that! A power amp failure is likely in your case. But it could also be your preamp.
Tube amps are generally not DC coupled, and they have output transformers which would block DC from your speakers and protect them. Such amps are very unlikely to be the culprit. So you’d likely either have a failed SS amp, or a DC coupled SS amp that is working properly but simply amplifying a failure from upstream (preamp).
Tube preamps often rely on output capacitors that block DC. These caps can fail over time, and leak DC. So if you had (say) an older tube preamp into a big DC coupled Krell amp, that could be bad news - the leaked DC from the preamp would be dutifully amplified by the Krell, and yes this could very easily fry your speakers.
Audiophile tube preamps have used lots of exotic film caps over the years, and not all of them have the best track record for reliability & longevity. I think Jensen oil caps were a problem at one point? Lower end preamps might even use electrolytic output caps (bad for sound, poor longevity), and those can definitely go bad.