Why did chávez have such widespread support when he first ran for president of venezuela?

Because he held out hope for the large masses of poor people (the majority) for a better life with much improved housing, education and general living conditions with his socialist/nationalist model the opposite of the governments that Venezuela had had since time immemorial selling out the country's natural resources to foreign companies with no benefits for the majority of the people.  

Increasing the release of greenhouse gases and pollution