What was Walter Cruttenden's biggest mistake during his journey with Acorns?

Walter Cruttenden identifies hiring the wrong people as his most significant mistake during his Acorns journey. He explains that giving someone too much authority without proper oversight can lead to wasted resources on poor marketing campaigns or bad investment decisions that an experienced person would have avoided. These hiring mistakes often resulted in poor capital expenditure decisions and mismanagement of resources. Cruttenden emphasizes the importance of understanding your industry before launching a business, as there are already enough challenges to solve without adding the disadvantage of industry inexperience. This insight highlights the delicate balance between trusting team members and maintaining appropriate oversight in a growing fintech company.