Why political context is key in determining the parties interest groups choose to collaborate with

When interest groups choose to collaborate with political parties what determines the type of party they opt to work with? Anne Rasmussen and Simon Otjes write that the two key elements shaping this decision are typically the ideological similarities between the interest group and the party, together with how powerful the party is in terms of its role in government. Outlining a comparison of more than 750 Danish and Dutch interest groups, they note that the extent to which these two factors affect collaboration between interest groups and parties is dependent on the characteristics of political systems