She made the mistake of running for a third term. No one in an executive position should serve more than two terms. I can recite a long list of successful two termers who failed in their third term- Stephen Harper, Mario Cuomo, Ed Koch, Tony Blair, Thatcher, the list is long. If you can’t get it done in two terms you won’t get it done in the third. You’ll just have restless, ambitious people who want you out and a populace that is tired of you.
I don’t think the populace was tired of Thatcher.
The biggest cause behind her ouster was the European Union (then called the European Community), which she dared to criticize, and correctly.
That is, her criticism of the EU/EC was correct.