Should it? If it was real world infrastructure, like a bridge it'd be easier to say that it belongs to those who lead the project and those who put down the money

The nice thing about a CC0 work is that it belongs to everybody. The leaders of the project have the same rights to use and modify the software as they do with software they have exclusive copyright over. In fact copyright does not grant the rights holder any new rights they did not have, it only restricts the rights of other people.

it probably already is in the public domain under US law, this just gives it the same status across jurisdictions