At minimum, with hindsight always being 20/20, the Minnesota Vikings miscalculated J.J. McCarthy's readiness to be an NFL starting quarterback. Three separate injuries this season have thrown wrenches in his development process, and a young quarterback's development often isn't perfectly linear anyway.
Until a Day 3 draft trade with the Seattle Seahawks for Sam Howell, the Vikings watched capable veteran signal-caller after capable veteran signal-caller sign elsewhere in free agency last offseason. Then, when Howell couldn't clearly beat out Max Brosmer for the No. 2 spot on the depth chart, he was traded in late August, and Carson Wentz was signed off the street to be McCarthy's backup.