It was financial smoke and mirrors. It worked short term and couldn't work long term. The effect of the decisions Jack Welch made sowed the seeds of GE's destruction. It's why his chosen successors couldn't maintain it. It wasn't maintainable.

It's the same reason it's stupid to say things like "the economy was good when President ______ was in office." The feedback loop is long. You can throw gas on a fire and it will look like it's roaring and hot for a short time. But there are long term consequences.