They also have (had?) a very active ballistic missile program, and have conducted implosion experiments.
The constellation of evidence is quite clear: Iran is a threshold nuclear state with all the pieces necessary to credibly threaten the region (and soon the US homeland) with nuclear weapons.
We've gone from, "The amazing Islamic Republic of Iran isn't even capable of building deliverable nuclear weapons and they have lots of peaceful reasons to do enrichment to 60%!" to "Yeah OK, they are capable and they are indeed enriching Uranium for their weapons program--hey, look over here! USA and Israel!!!"