I wouldn't have classed a 4-gang dimmer at £40, which promised intelligent overload protection and soft-start as cheap.Cheap dimmers tend to act as expensive fuses and a cheap dimmer will always fry long before a fuse will blow.
Nor would I have expected a failure of a 60W fused GLS lamp, one of a pair on one gang (rated at 250W) to catastrophically destroy the module.
But it did. Twice (i.e. I lost 2 modules in the same way).
The previous dimmer switch was a cheap one (unbranded one bought from Wickes, IIRC), and that lasted well over 20 years and survived countless bulb failures with never a murmur. I only replaced it because cosmetically it was looking tired - wish I'd kept the gubbins and bought new knobs and a 2G blanking plate.