Student loans are not large enough to matter in the regard you're referring to. The housing market mess was at least 30 times larger than the student loan mess.
Most student loans are in the government's hands, most of the interest goes to the Federal Government, not to eg JP Morgan or Bank of America. The US financial system has minimal exposure to student loans and the default problems.
You're talking about $400 billion of present high risk default potential. The housing market crash wiped out ~$25 trillion in paper wealth just in the US, including in the stock market. American wealth dropped by 40%.
That drop would be equal to $40 trillion today. The entire student loan market is $1.4 trillion, a fraction of that is a default problem.
The Fed was running $85 billion per month QE programs just to stabilize the housing market.
If it were necessary, the Fed could fix the student loan mess in six months of casual QE.
The 2008-2010 great recession took down dozens of global banks, including making two of the big four in the US insolvent. Dozens of large corporations from around the globe required short-term Federal Reserve loans to remain operational as the global monetary & banking system froze.
Student loan defaults are a $50 billion per year problem. The loaned out money was conjured out of thin air by the Fed and US Government (which does not have a surplus to lend); the interest being paid is paid on that same magic money. The Fed shovels large piles of cash back to the US Government every year. If they need $300 billion to fix it, they've got more magic money (ie the Fed will debase the dollar and 0.2% of the value of all dollar assets globally and they'll do a program with the US Treasury).