well i guess i could have a try to explain: it's like someone who grow to be in some way under a certain circumstance. the years around 1600 was all of floods, coldness... which leaded to poor harvests and rising prices. so what shylock loves is just money. but he did suffer a lot from the christians, cause he was jewish.

That means that Shylock is a cruel person, but his cruelty may be explained by the evil he experienced. The author tries to justify him.

Shylock is a' creation of circumstance', when he talks about his single-minded pursuit of a pound of flesh and his frequent mentions of the cruelty he has endured at Christian hands

It means, the situation Shylock was in is what caused him to be who he is. Basically saying it's not his fault.