Celtic made the semi a few times I think? Even the final once?
In the 90s when Leeds hit the big time with Kewell, Viduka, O'Leary and did well in the UCL they went nuts and bought expensive new players and it nearly bankrupted them, they flopped, relegated, and just made it back to the top level after 25 years or so out in the lower leagues. That was mismanagement of course, but it's high stakes either way.
Leeds' problem then was that they bought average players turning them into expensive players. That one CL Semi appearance ruined the club. They spent everything they had, and didn't have, chasing the $ the CL gives clubs. I'm surprised Ridsdale wasn't hanged in City Square