There was a massive international financial crisis that outed the Labour government and brought in a Tory/Lib Dem coalition government based on promises of government austerity.

There was an independence referendum in Scotland where the main campaign point for staying with England was to ensure they stayed in the EU etc.

Then the Tories managed to pin the blame for the failings of the coalition on the minor partner and drew a line under that for the next election.

Then there's brexit, which was really a vote to put an end to bickering inside the Tory party. But the population, narrowly voted to leave the EU! This was very much a protest vote.

Then there's a utter crazy story of quick rotation of prime ministers and scandal and sleeze and very very poorly-received budgets and things.

So then this year Labour are back, and their main strategy was 'at least we're not the Tories'. They are not popular, but they are not the incumbents.