In The Pillars of the Earth what circumstances created Tom Builder's extreme poverty?
In Pillars Of The Earth, Tom Builder is a master-mason/builder; in Chapter 1, we find that he turns down the lucrative and possibly life-long job of builder to the Exeter Castellan (governor of a fort or castle) for the chance to build another cathedral. His wife, Agnes, has never forgiven him for what she considers an irresponsible decision.
As the story starts, we find him working on a house for Lord Percy Hamleigh's son, William Percy. William is engaged to the Lady Aliena, daughter of the Earl of Shiring. The house is to be a wedding gift to both William and Aliena. When William makes a sudden visit to the work-site, Tom knows this calamitous event forebodes no good thing, especially as he finds out why William is there. Tom finds out from the young squire who precedes his master that the Lady Aliena has rejected William as bridegroom. Tom is flabbergasted and knows in his heart that his livelihood and that of all the masons who are working with him are at stake.
When William finally rides up and tells Tom to dismiss his men, Tom bravely and stubbornly insists that William pay all of the master masons a full week's wages for the work already completed. Although William complies, he is not happy. Tom and his family stay in the village to work in the fields during the summer. They save up enough for a pig. It is the loss of this pig coupled with the loss of his work on William Percy's house that plunges Tom Builder's family into extreme poverty.
When the pig is stolen by an outlaw, we find out that
They had bought the pig in the spring, as soon as they had saved enough pennies, and they had been fattening it all summer. A fat pig could be sold for sixty pence. With a few cabbages and a sack of grain it could feed a family all winter and make a pair of leather shoes and a purse or two. Its loss was a catastrophe.
The family are now so poor that when Tom's wife, Agnes, dies from childbirth, Tom leaves his own baby on Agnes' grave as he has no means to provide for its survival.
A page-turning novel to be sure. Thanks for the question!