Why do we sell weapons to Saudi Arabia if it ends up going to ISIS a year later?

that's not true. Saudi Arabia has suffered alot from ISIS and wages a war against it.
look it up. the number of attacks by ISIS against saudi arabia is higher than any other country.
so you should ask your friends in Iraq how did ISIS got US weapons

Money. And also the fact it isnt supposed to go to them but it does anyway. I understand your reasoning. But money is the main reasoning.

Ask their pals the Bushes.

Money

ask hillary.