In the late 1980s, what caused the rehnquist court to start to restrict congress's ability to regulate various areas of the economy?

changes in the composition of the Supreme Court.  

This was largely due to efforts of President Reagan whose appointments of Justices to the Supreme Court made the Court largely conservative. This includes elevating  William Rehnquist, to the position of Chief Justice in 1986 when Warren Burger retired

it would have concentrated power in the executive branch of the government. it would have restored balance among the three branches of government. it would have set a precedent for government intervention in the economy. it would have signaled an end to all the programs of roosevelt’s new deal.

did this .