He wanted to be noticed and appreciated. When Spidey first met him (by saving him), he felt that and immediately believed him and Spider-Man were best friends.
After he got that delusion in his head, he had a different approach to anyone new he met (like Gwen, as an example) and was a lot more cheerful until his bad luck continued (the accident).
All he wanted after his accident was help and his friend that he believed he had, and when his friend stole what was so important to him (to be noticed), he felt betrayed, hurt and immediately turned on him.
Electro also put people in danger at first unintentionally, as he couldn't control himself. "It's not my fault."
After that whole debacle, he concluded that people should live in a world like he did -- darkness (hence the blackout).