"401ks exist to help people save for a secure retirement, not gamble on speculative assets," said an industry observer.

What to know:

• "401ks exist to help people save for a secure retirement, not gamble on speculative assets," said Lee Reiners of the Duke Financial Economics Center.

• "Last week, we did not get out quickly because fundamental data still looked strong," said BlockTrust IRA, an AI-driven fund provider working with pensions.

• Tokenization and smart contracts are reimagining the future of the retirement industry, says Franklin Templeton.

Bitcoin's 50% plunge from its October peak has done more than just erase $2 trillion in market value — it has reignited a fierce debate over the fiduciary math of the American retirement system.

As investors scramble to parse the drivers of the latest crash, industry observers are asking if volatile digital assets have any business being in a $12.5 trillion 401(k) market designed for stability.