The reason for the 32A MCB (miniature circuit breaker) not tripping and the 80A RCD (residual current device) tripping is due to their differing designs and duties.
The 32A MCB is a pure overcurrent device and will not trip until the current through it exceeds 32A e.g. live to earth, live to neutral or too many appliances switched on, many are designed with an overload factor often to allow for the higher current flow as motors (fridges, hoovers) start as well, so it could be a figure slightly higher than 32A.It will only be connected into the live conductor.
The 80A RCD will also have another setting (usually 100mA (milliamp i.e. .1 amp) for a main unit) These devices are connected to both the live and the neutral conductors.
Again it is designed to protect from overloads above 80A, subject to the comment above, additionally it also measures (simple explanation) the difference between the current flow in the live and the neutral. If these values differ by more than the 100mA owing to a fault between the live and earth or between the neutral and earth the device will operate.
So your slug in the socket though not causing a live to earth fault in excess of 32A was causing one above 100mA.
Of course if you use mains power tools outside you should connect them via a 30mA RCD socket or adaptor.