Final answer:
Large-scale healthcare reform was halted in the 1990s due to strong public opposition and political strategies, including a negative ad campaign and policy disagreements, which resulted in a lack of necessary support in Congress.
Step-by-step explanation:
The primary reason why large-scale healthcare reform was not implemented in the 1990s can be attributed to public opposition and a lack of political will. During the Clinton administration, despite initial support from various institutions and figures like C. Everett Koop, the Health Security Act faced fierce opposition. Political opponents criticized the plan, labeling it 'Hillarycare' and decrying it as an excessive expansion of government powers and a step towards socialized medicine. This was further compounded by a successful negative advertising campaign funded by insurers, drug companies, and other medical industry stakeholders that played on fears of decreased innovation and quality in healthcare.
The lack of support was not solely from the conservative side; there was a general bipartisan reluctance to enact the proposed reforms. All this culminated in a significant Republican victory in the midterm elections under the banner of the Contract with America, effectively ending healthcare reform discussions in Congress. In summary, a combination of strategic political opposition, well-funded negative campaigning, and the looming midterm elections all played decisive roles in preventing large-scale healthcare reform in the 1990s.