Shares of C3.ai have been falling sharply since news of the resignation came out.Whenever there's a change in management, it can mark a turning point for a company, especially if an executive has been in charge for a long time. It gives a business the opportunity to have a fresh set of eyes to look over the operations and potentially make strategic changes. But it can create a lot of uncertainty in the short term.Recently, C3.ai (AI -2.38%) announced that its CEO, Tom Siebel, will be stepping down for healt ...