Some raised their eyebrows when Pic, 22, agreed to switch from Marussia to Caterham - both similarly-matched backmarker teams - for the 2013 season.
"We were very pleased with the collaboration with Marussia," Panis insisted to the Russian website f1news.ru.
"But for the future we wanted to have a serious partner, and when a company like Renault wants to work with you - we hope for many years - it is impossible to say no," added the former BAR and Toyota driver.
"So this was the main reason."
Meanwhile, Panis said Pic is happy to be paired with Giedo van der Garde this year, after the highly experienced and rated Heikki Kovalainen was ousted.
"Last year Charles learned a lot from Timo (Glock), so now I think that factor is not so important.
"Personally, I don't mind. An experienced teammate is fine, but we are happy with Giedo. He also deserves a chance to show what he can do," said Panis.