We didn't have universal health care before CU either. It wasn't included in the ACA, before CU. It failed when Clinton tried in the 90s, and it failed every other time anyone tried before that too. You are just using Citizens United as a bogey man for a policy you don't like. You can complain about Trump all you like, but Harris didn't have much less dark money than he did. And Clinton / Biden had double what Trump did in 2016 and 2020. https://www.opensecrets.org/2024-presidential-race
Universal health care wasn't as popular back then as it is now, so that's to be expected:
https://news.gallup.com/poll/4708/healthcare-system.aspx
This isn't about who wins campaigns -- this is about who influences the issues they campaign on. Since the Citizens United decision politicians have had to switch to the Super PAC model to be competitive, which gives drastically more power to dark money donors. And unsurprisingly, as cited in that study, the influence of average citizens on politics has been completely surpassed by businesses and economic elites:
https://www.cambridge.org/core/journals/perspectives-on-poli...