"People" in this case is a legal term, not a colloquial one. Nobody's arguing that corporations are not composed of people.
replyAnd, arguably, yes, the same argument applies to the legal personhood of a forest - that proving that the impact on a group of trees aggregates to something significant and legally actionable is unnecessarily time consuming to keep doing every time someone tries to argue their clear-cutting operation hasn't actually harmed anyone, so you assign legal personhood to the forest so you can say "you harmed the forest" in the same way you can say "you harmed the corporation."
A corporation is a single legal entity with distinct rights and obligations, that’s the entire point of incorporating, so you don’t have to create a fully connected graph of agreements between people, you can group them into entities that can then enter into agreements. The fact that corporations then have some rights similar to those of “natural persons” is the legal fiction referred to.
replyRight - you can sue CorpCo for violating the law, you don't need to dig in far enough into the corporate structure, decision logs, and personal actions to figure out that Bob, head of accounting for CorpCo greenlit the budgetary plan for Project Alpha, which makes Bob an accessory to the actions of Jim, who signed the contract to the subcontractor who performed the illegal digging operation, who therefore is responsible for incentivizing the violation of the law by way of making false statements about the status of the permitting process, and therefore both Bob and Jim must each pay damages, as must Tracy, who was aware that the permitting process was delayed (and even brought it up in meetings), but didn't contact the regulator when she should have.
replyNow, the fact that we've also agreed that corporations can act as political actors is fucking stupid, but the intent behind corporate personhood is that without it, it's effectively impossible to hold corporations accountable in any kind of reasonably efficient fashion.