Why did the Liberal landslide of 1906 catch people by surprise? What were the Liberal issues that attracted voters to the Liberals? Why? Did the issues have anything in common, or was it an accidental convergence of unrelated issues that led to Liberal victory?

The main issue at the 1906 General Election was free trade. The governing coalition of Conservatives and Liberal Unionists was split down the middle by the issue. Some argued for free trade, but others like Joseph Chamberlain favored protectionism, or Tariff Reform as it was called. The Liberals were able to exploit divisions in the governing coalition, maintaining a consistent position on the issue of free trade. They argued that free trade would keep prices low, especially for basic goods such as bread. This proved to be a particularly attractive measure for the working poor and lower middle-classes.
The Conservatives had been in power for quite some time, and inevitably many thought that it was time for a change. Although free trade was the main issue during the election campaign, it was not the only one. There was a general sense that the country was facing a number of pressing problems which urgently needed to be addressed, and that the Unionist coalition had neither the energy nor the ability to deal with them.
The Unionists had benefited greatly from patriotism during the height of the Boer War. But the aftermath had revealed some uncomfortable truths about the conflict. The use of concentration camps by the British to house Boer civilians was hugely controversial, especially among the educated middle-classes. And the appalling physical condition of many British Army recruits highlighted the terrible effects of urban poverty and undernourishment.
The Liberals were able to win their landslide by successfully building a coalition of different interest groups—labor unions, working people, Non-Conformists, educated professionals—that proved unbeatable. On almost all the major issues, whether it was free trade, the Boer War, or national education policy, the Liberals were able to appeal to a much wider base of support than the Unionists.
Though different in some respects, the various issues highlighted during the 1906 campaign all had one thing in common—they struck a chord with each and every sector of the Liberal Party. The Party had been a rather unstable coalition of interests for a number of years, and it was this very instability which had ensured Tory dominance in government. Yet the key issues of the 1906 campaign came together fortuitously for the Liberals, allowing them—temporarily at least—to reunite the disparate elements of their coalition to form a united front against a different kind of coalition—the Unionist coalition—that had become even more fractious and unstable than the Liberals had been in the recent past.