In the 1200's there was a system where the Jews loaned money to knights and landowners under the protection of the King, and this worked fine until Henry III extorted almost £100,000 after he failed to get Parliament to agree to give him a nation wide tax.
This destroyed the prosperity of England's Jews - who were previosly the most prosperous in Europe. To meet the Kings demands for money the Jews were forced to sell thier loans onto others for discount. The people who bought the loans were English nobles - and even both Henry III's and Edward I's Queens - who then demanded payment of the loan straight away and when the knights and landowners failed to pay thier land was declared forfeit.
Naturally, this caused widespread discontent amungst the lower classes and they sought someone to blame and the Jews were the easy target.
When Edward was preparing for his Crusade he needed to raise money but the Knights and Landowners in Parliament refused to allow a tax to be issued unless their grievance with the Jews was dealt with. Edward thus proposed that Jewish moneylended be restricted and that no debts be sold on without permission of the King but the Knights and Landowners were not impressed because they had seen similiar proposals from Henry that came to nothing and the Nobles opposed it because it would stop them from easilly aquiring land. He eventually got his tax when Henry enforced restrictions on Jewish moneylending
When Edward became King he was once more facing a major financial trial. He was heavilly in debt as a result of both his Crusade and Henry III's building projects and needed to raise money immediately. This meant turning once more to the Knights and Landowners. To appease these men he banned Jewish moneylending but the heart of the problem was actully Christian Nobles buying Jewish debts and taking land for themselves. In banning the Jews from lending money Edward sought to appease the Knights and Landowner by picking on the easy target that the majority wouldn't care about.
Between the 1260's and the 1290's Edward had attempted several different solutions to appease the Knights and Landowner and to allow the Jews to live in his lands still under his protection - he had told them that they should live by "honest" means as traders, shop-keepers, farmers, etc but this was impossible in England at the time due to the prejudice against the Jewish people - but his actions had been ignored. The Jews continued to lend money, the Nobles continued to buy up the Jewish loans and the Knights and Landowners continued to lose their land to unscrupulous Nobles.
He was fed up with the problem as it not only hampered his effective governance of the country it was a major stumbling block whenever he needed to raise money - and the wars he engaged in and his plans for a new Crusade meant he was almost constantly in need of money. The problem was that he could expell the Jews and appease the lower classes thus making it easier for him to get taxes passed but at the expense of losing a historically reliable source of income in its own right. The dilema was solved when someone pointed out Charles of Salerno's solution of asking for a tax to recompense him for expelling the Jews from his own lands. The English Knights were so pleased when Edward expelled the Jews that the tax they consented to raised £116,000 which was the biggest tax ever collected in Medieval Britain, and the Church was so pleased with it that they consented to a tax of thanks to be passed that same autumn.
Edward's need to raise taxes meant that the expulsion of the Jews was inevitable, and not only was it inevitable it was undoubtly the most popular and well recieved decision he ever made as King. The Jews were never popular but until Henry III began extorting money from them in great quantities they had been seen as a necessary evil, but as a result of Henry's actions Edward inherited a situation that could not be remedied, the Knights and Landowners had stopped seeing the Jews as a necessary evil and started seeing them as a cancer that should be cut loose.