The First World War took much of Wilson's focus on foreign policy during his time in office. On one hand, an argument could be made that Wilson held a legitimate fear that democratic nations, and democracy itself, was placed under great jeopardy during the First World War. The forming of secret alliances and level to which animosity had grown in Europe made it a situation where all other concerns, such as domestic, dwarfed in comparison. This could be proven with Wilson's desire to create a configuration of world orders such as the League of Nations afterwards that sought to maintain harmony after the war was fought. Another line of logic would suggest that pursuing the end of war was extremely profitable to businesses and other industrial interests, and to continue this foray helped in these domains.
Woodrow Wilson was a Progressive who simply got distracted and hyperinvolved in world affairs. As catastrophic and unprecedented as World War I was, it was impossible to ignore. Our best trading partners were involved in it up to their gills, and needed our help to win, so Wilson had a huge stake in both the outcome and the aftermath. This overshadowed the desires he had to pursue further reforms at home as a Progressive.
True, Progressive amendments like the 17th, 18th and 19th were all adopted during this time, but Wilson had little to do with that, nor the time to try.
It really makes a lot of sense that Woodrow Wilson would have split his time like this. After all, he was the president of the United States during a big time in foreign affairs.
First of all, he had to deal with the issues of World War I beginning in 1914. He was trying to figure out what role the US would play in the war. First he worked to keep the US out, then, when the US was in, he tried to shape the war aims of the Allies.
Second, he had to deal with the issue of the peace treaty -- the Treaty of Versailles. He had to work on negotiating it at first and that kept him outside the US for a long time. Then he had to try to push it through the Senate.
All of this took up his time and he did not have enough time or energy left over for domestic affairs.