This is the testimony of one of the primary authors of the current NIE, from less than five months ago.

After terrorism, the ongoing efforts of nation-states and terrorists to develop and/or acquire dangerous weapons and delivery systems constitute the second major threat to the safety of our nation, our deployed troops, and our friends.

The time when only a few states had access to the most dangerous technologies has been over for many years. Dual-use technologies circulate easily in our globalized economy, as do the scientific personnel who design and use them. As a consequence, it is more difficult for us to track efforts to acquire, for nefarious purposes, these widely available components and technologies.

Iran and North Korea are the states of most concern to us. The United States’ concerns about Iran are shared by many nations, including many of Iran’s neighbors. Iran is continuing to pursue uranium enrichment and has shown more interest in protracting negotiations and working to delay and diminish the impact of UNSC sanctions than in reaching an acceptable diplomatic solution. We assess that Tehran is determined to develop nuclear weapons—despite its international obligations and international pressure. This is a grave concern to the other countries in the region whose security would be threatened should Iran acquire nuclear weapons.

What changed since then? Apparently some radical new information has come in, or something else is going on, and of course, something that hot would not be made public.