Shares of Credit Suisse surged 7.5 percent at the session open on Tuesday following the news, while Prudential's stock slumped 3 percent.
"By definition you want to leave when everything is going well. There's not one business slowing down or having any issue," Thiam said on his departure from Prudential. "That really allows you to leave without the market worrying that you're running away from something. That was really important."
He added that Prudential has a "very good" succession plan in place. "It's a kind of formality but it hasn't been announced. It will be announced shortly … we will reassure the market," he said.
Paul Manduca, chairman of Prudential, called Thiam an "exceptional leader" who had steered the company through the financial crisis. Predecessor Dougan added that he had "tremendous respect" for him.
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Thiam joined Pru as its chief financial officer in 2008 and was appointed group chief executive a year afterwards. The London-based international financial services group has operations in the U.S., Asia, Europe and Latin America and its shares have risen around 150 percent during Thiam's tenure.
Onlookers cite this background in insurance and wealth management as the main driver behind his appointment at Credit Suisse. Christopher Wheeler, an analyst at Atlantic Equities, called it a political move, as the bank is replacing an investment banker with Thiam in the hopes of appeasing anxious Swiss authorities.