Calls to break up global banks grew quieter as profits revived and Europeans finally grasped the nettle of deep restructuring—but it couldn’t last.

Credit Suisse , part-way through a multi-year overhaul, has a new activist investor buzzing around. Full details of the plan from RBR Capital Advisors, a small Swiss investment firm, are to be published later this week, but it has been talking to the bank about a three-way split into investment banking, asset management and wealth management firms.

It is an odd time to make this move. Credit Suisse’s stock is still far below its value when Tidjane Thiam became chief executive in 2015, but the shares are up almost 20% since its $4 billion rights issue closed in June.

Mr. Thiam appears to be winning shareholder support for his plan, despite early missteps and cuts to profit targets. Compared with rivals Barclays and Deutsche Bank, which are both facing questions about strategy and leadership, Credit Suisse has made progress.

However, its position is far from secure and RBR would be right to point out inconsistencies in what it does. Like its two European rivals above, it has continued to shed revenue and lose market share to U.S. peers in investment banking—only partly deliberately.