[PBO]

The photos don't show the crack in detail however it looks to have failed suddenly (unlike pinkpanda3310's mangled mess) because it's 'bright'

IIRC the chassis is 3mm 7075? Assuming the chassis material is in fact 7075 of consistant quality, here's a theory or 2...hard anodising 7075 in black can have mixed results & this can be a simple as mixed grades in the anodising bath...this may result in the 7075 parts being stripped & reanodised, which would typically produce a product that is thinner than original

Or the harmonic resonance may have been matched exactly through vibration from the drivetrain & amplified through the long 'tongue' at the same time as impact...resulting in the failure

Or the 7075 has been tempered & is stretching past it's capacity (I've often thought the RC8T chassis 'tongue' was suspect at this point just going on how it looks) which results in failure

I think first or second are more likely...assuming the material is correctly labelled & manufactured