To date, Iraq has deposited money in exchange for electricity it receives from Iran in a local bank that was subject to American supervision and allowed Iran to use the money only to purchase food and medicine.
 
What has changed now? The Iranians take advantage of the heat wave and reduce the current of electricity to Iraq, which leads to power outages and internal unrest there. The US defined this Iranian activity as "blackmailing" Iraq. 

Despite everything, and in order to maintain stability in Iraq during this summer, the Americans approved this relief which will bring in at least hundreds of millions of dollars to Iran in the near future.