I was reading about the construction of the tower of London on wikipedia, when I came across this bit:
Land was confiscated and redistributed amongst the Normans, who also brought over hundreds of Jews, for financial reasons.[67] The Jews arrived under the direct protection of the Crown, as a result of which Jewish communities were often found close to castles.[68] The Jews used the Tower as a retreat, when threatened by anti-Jewish violence.[67]
And the reference is:
Parnell, Geoffrey (1993), The Tower of London, Batsford, ISBN 978-0-7134-6864-9
What was meant by "For financial reasons". Did the Norman ruling class really ship over hundreds of Jews just for 'Financial Reasons', and if so, why would they do this?
So it's not quite them "shipping over" large numbers of Jews. What actually happened is they more-or-less invited Norman Jews to migrate to Britain as the Normans did. This was not unheard of in Medieval times (though note that this means several instances over centuries, so still not a super-common thing), the most notable example being the invitation for Jews to settle in Poland.
As for what the financial reasons, Jews were an important part of Medieval economies, mostly because they could lend money (many Christian societies restricted usury, the lending of money at interest, but these restrictions didn't apply to Jews) and had experience doing it. It was advantageous to the Normans to have access to credit so they could borrow money.
But, Jews also had other important roles for an economy. They were heavily involved in trade, including long-distance trade. This could help a local economy's goods be traded both to nearby towns and to farther-away places.