It's clearly caused by bad weather. Iran didn't want him dead. Israel did but I don't see a scenario where they could have done something.
I don't think you're right,Iran president is the Most hated ruler in the middle East,he is a Tyrant and a cruel leader,the people of iran never loved him. He has been backing and financially supporting Several Islamic Militants/rebels that are causing havock/destabilizing the middle East. I think it was an assassination,the Israeli and United States might been responsible for his death. Afterall who want a cruel leader to lead them.