That is greatly exaggerated.
The story starts with temperature dropping in winter this year (I believe -20 C was the lowest) the usage of natural gasses shoots up as people use it to warm their homes, there is a shortage so the power plants switch to burning liquid fuel (more specifically mazut) which creates pollution to the point where the levels enter dangerous territory, power plants shut down part of their operation, it causes blackouts.
Who is the easiest to blame? Bitcoin miners! And it is not all lies because there has been an increased number of miners in Iran and they have been putting some pressure on the network. But as I said it is greatly exaggerated.