I see so a place to keep those units temporarily
It effectively was a storage space I suppose as some locomotives remained there 20 odd years.
However it was a scrapyard and was never intended to be a temporary storage area.
The reason 200 odd steam locomotives were saved wasn't due to design or a soft spot for preservationists or anything like that. It was purely down to circumstance and luck.
British railways were changing in the 1960s. As well as steam locomotives being phased out, so too were traditional wagon hauled trains and marshaling yards.
Woodham's scrapyard had a load of wagons to scrap as well as locomotives. Locomotives were difficult and timely to cut up, whereas wagons were cheap and quick to cut up. The idea was to get through all the wagons and make money quickly, leaving the steam locomotives as a kind of retirement nest egg for a later date.
It just so happened that this gave preservation groups enough time to raise funds and save their chosen locomotive. As long as they met the scrap value, he was happy to sell. However, much like some modern groups who set up crowdfunders that raise nothing, there were groups then who appeared to never look like raising money yet expected a locomotive to indefinitely be kept aside for them. He did cut up some engines to sharpen the minds of other groups...
This was in contrast to other scrapyards, who cut up engines straight away.
I believe there was a scrapyard in the midlands somewhere that was similarly important for diesel preservation. It specialised in removing asbestos, so there were plenty of scrap diesel locomotives available who had already had their asbestos removed.