Once again you can thank a weak Democrat US president, this one in 1979, for making Iran what it is today.
What specific Carter policies made Iran what it is today?
The Carter presidency was “bookended“ by Nixon’s Watergate affair and Reagan’s Iran-Contra scandal.
When Carter became president, the US met its energy requirements by importing 50% of its total oil requirements; that dropped to 40% when he left office.
His deregulation of the natural gas industry was what kickstarted the growth of the domestic oil and gas industry.
Carter, not Reagan, began the deregulation of the American economy.
Deregulation of the airlines, trucking and railroads introduced more competition in those sectors.
He brought Egypt and Israel to the peace table and that treaty still stands between those two countries.
He set aside huge swaths of Alaska for preservation and that are still preserved to this day.
He made the politically damaging decision to appoint Volker as chairman of the federal reserve and refused to interfere when Volker squeezed the money supply and jacked up interest rates.
Kissinger and Rockefeller (the banker) wanted the deposed shah brought to the US, and made a false case that the shah could only be treated for his cancer in the US.
Carter was against having the deposed shah find refuge in the US, asking the very question of what happens when the embassy gets overrun.
Anyhow, I suggest you read
The Outlier by Kai Bird; the whole 779 pages including the bibliography and the notes. Not Wikipedia. Not some three sentence summary, the whole thing.