The question is, why did they bother to take it to court instead of just transferring ownership directly to their persons and then voting as humans? If corporations are just proxies then why bother with the lawyers and the court fees and the time?
Because they want the other benefits of the corporate form. Why should they have to choose between the benefits of the corporate structure and exercising the rights the municipality has given property owners?
They're not, and the terminology shouldn't be confused. "Juridical people" tries to sneak in priors about what "people" means.
People, of course, have rights. Corporations are not people, including "juridical people". They are legal fiction with absolutely no rights. Every action they take is permission granted to them by the people.
You have it backwards. As you acknowledged elsewhere, "juridical people" is an abstraction over a group of people. To be more precise, a collective acting towards a unified goal (with a set of norms binding them together).
Even the naive perspective over this recognizes that the corporation has "rights" by being proxies of their constituents, so you are correct in saying "Every action they take is permission granted to them by the people."
However, a more careful analysis recognizes that the exercised rights of a corp comes from a combination of the rights of its members, often in intermingled way (due to binding norms of the corp) that doesn't map directly into a singular individual. As such, it's common to abstract it as the "rights of the corporation". You can look at the individual rights (sometimes you have to), but that's like looking at humans by their individual cells. Certainly doable, but cumbersome most of the time.
Also, I find the phrase "They are legal fiction with absolutely no rights" funny. As if rights weren't legal fiction themselves. Not that this means much either, ethics and law are about "what ought to be done", and that's - objectively - as fictional as you can get.
The one that backs the law, for instance. But, more broadly, corporations, specially ones ruled by shareholders/contracts, tend to have a will of their own, and "people" in ethics is more about will and desire than biology.