That's not what CU held. The idea that corporations have legal personhood with some degree of rights is much, much older than Citizens United.

Citizens United was a non-profit corporation that created Hillary: The Movie which was critical of Hillary Clinton. They wanted to distribute it shortly before the 2008 primaries. The Federal Election Campaign Act prohibited corporations from using general funds for electioneering or speech that advocates for the election or defeat of a federal candidate within 30 days of a primary or 60 days of an election.

The Court held that the First Amendment prohibited the government from stopping an incorporated association from independently spending its own money for political advocacy of a candidate. To put it another way, if I can spend my money to advocate for or against a candidate, why can I not get together with some friends to pool our money and incorporate to do the same? If this had gone the other way would you be okay with a corporation being forbidden from releasing a video critical of Trump shortly before the 2024 election?