Iran is a sovereign country able to set their own targets. They are members of the IPCC but deliberately chose non-participation for 15 years up to 2023. Furthermore, they had unfettered access to Chinese solar panels and wind turbines until recently. As they are the main supplier of oil for Chinese teapot refineries, trade for solar panels would have been simple.

Iran bears full responsibility for their outlier status no different than the current US regime.