Foundation Pilling

To make a the aches and pains of the previous excavation go away!

Ditto

Presumably because the piles go much deeper than the excavation?

It is not always the case that piling is before excavation.

However, when it is, a good reason is that it is easier to pile from ground level than from in a hole. For instance, how big a crane do you need to lift a piling rig into an excavation? It is cheaper to pile and then do the digging.

from what has been said the assumption is clear

if your moving a piling machine around a building site, its easier to move ove flat land than to move over land with lots of holes in in it

obvious really

We don't start always with piling before excavation in general practice. where it needed we do exactly the same what you ask.