Every year, hundreds of thousands of Asian students (~90% Indian and Chinese) flock to US universities for grad studies. They work hard, get a good GPA and want to continue their stay here. When they apply for jobs, the pool is very very limited because not all companies want to carry the burden of VISA/lawyers/immigration etc.
Oracle is one of the handful of big firms that feed on such students. They have the capital and resources to carry the immigration burden. And they hire students in bulk. I personally know a lot of students-turned-Oracle employees from all major universities.
At that point, the students just want to stay in the US legally, salary takes a backseat. They know the fact that if they can stay for long, money will eventually come.