How so? An economic crisis doesn’t mean the end of the economic system. It just means that things will get much worse. Which means that in their desperation the people will call for extreme measures to fix things. This often leads to reforms, not revolutions. Or it doesn’t, and people just accept that things have gotten worse, because they are too busy trying to survive rather than questioning the system.
So, an economic crisis is a chance for political change. But this change needs to be prepared well in advance, otherwise the people won’t even consider that particular way of change and demand political measures that typically make things even worse.