From the introduction in your first link:
Through reviewing the existing studies, theories, and data behind the World Happiness Report, we find that the most prominent explanations include factors related to the quality of institutions, such as reliable and _extensive welfare benefits_, low corruption, and well-functioning democracy and state institutions.
Under Welfare state generosity:
In a longitudinal study of 18 industrial countries from 1971-2002, Pacek and Radcliff examine welfare state generosity by using an index capturing the extent of emancipation from market dependency in terms of pensions, income maintenance for the ill or disabled, and unemployment benefits, finding that welfare state generosity exerts a positive and significant impact on life satisfaction.[21]