>It also isn't nearly enough to make nukes

Enrichment % is very misleading. Natural is about 0.7%. 3.5% is halfway to 90%. The distance from 60% to 90% is tiny.

That's because the distance is calculated using the quantity of raw material that needs to be filtered and not the enrichment percent, the more pure, the less material needed, hence smaller distance to 90%.

>Right, they could, and didn't. Why?

Some people worked hard to ensure the latter would be very inadvisable for Iran. Being so close isn't a stable equilibrium though.