Given: companies have "free speech" like individuals -- as ruled by the SCotUS. Thus, they can pay market rates (however you define those) for political reasons, much like individuals. In this way, the public is greatly overpowered.
However, for a government public-comment period, there is zero entry fee, and I think we just need a couple of extremely simple rules to, ideally, prevent this from happening again:
1) A company/corporation must -- like individuals -- comment under its own name. No hiring others, period; the commenter must be your own employee with the authority to use the name of the company/corporation.
2) Again like individuals, each company/corporation gets ONE comment. No more. There's no money for commenting, so you can't buy more like political (election) influence.
(Yes, the C-suite residents -- and each employee** -- of each company/corporation can ALSO post under their own names, one post each, real names only.)
Enforcing these? Nigh to impossible, but I think we can all agree on principle, and that's a start.
** If the employees reuse the company's post, they must be allowed to post on company time. I would expect that for some larger corporations that many employees might choose to make a public comment that differs from their employer -- on their own time, of course -- and that right of free speech shall not be infringed and shall be without consequence by their employer (reprimand/termination).