I want to know what do you think?

What was probable cause?

Before that, for last 2-ish years I must replaced 5 LED bulbs.
No other symptoms.

Right before failure, one or two LED bulbs started blinking. I heard “scorching” sound.
And smell of burned electric/electronic (isolation).

Then I disconnected all circuits and opened all surrounding boxes…
Over-current breakers or RCD/GFCI didn’t tripped.

Extra photos:

(ignore temporary jumper - fixed now)