Student loans first became nondischargeable in bankruptcy in 1976 due to an amendment in the Higher Education Act. Section 439A of this act made student loan debt non-dischargeable until five years after the start of the repayment period, except in cases of undue hardship. Over time, laws were tweaked and widened to reinforce this limitation.
Not that simple. This got started before he took office, and it culminated long after he was out of office. Way more than one person is to blame.
https://www.tateesq.com/learn/student-loan-bankruptcy-law-history