TL;DR: In the last year, the Wikimedia Foundation has fired several union organizers, including those that worked on the Community Tech team - a team dedicated to building features for the volunteer community that edits Wikipedia. As the Wiki Workers Union tries to get the Wikimedia Foundation to recognize their union, it is worth remembering that this is not the first time that the Foundation has worked against the community. Wikimedia Enterprise is a betrayal of the volunteer movement community of Wikipedia editors, as the Wikimedia Foundation is providing privileged access to big tech AI companies to the Wikipedia corpus - a body of work that the Foundation does not own. Movement volunteer communities contributed to Wikipedia under copyleft licenses - licenses that work to ensure that the work remains free (as in speech). The big tech AI companies do not license derivative works under copyleft licenses and often do not even attribute where the works came from. This means that volunteers are working for big tech for free, and the Wikimedia Foundation is selling privileged access to that free labor. It is against that backdrop that the current unionization struggle unfolds.
Fair point on using ToS.
Before Wikimedia Enterprise they weren't getting paid and the LLM companies may have had to depend on residential proxies
It is extremely cheap to rely on residential proxies and certainly magnitudes cheaper than Enterprise. The free infrastructure is absolutely not shoddy and I'm not sure why you think it is, though making all scrapers use it would probably make it shoddy.
If they were using the API, why couldn't WMF just revoke their keys?
The API has no keys. It's commons public access. If you want to revoke access, you'd have to identify the IPs and manually block them.
You're also still assuming this is violating intellectual property. Customers of Wikimedia Enterprise are forced to sign Terms of Use (accessible at https://dashboard.enterprise.wikimedia.com/signup/) that legally bind them to respect the license of the content even though, as you point out, they are already bound to respect the license. To maintain access to Enterprise, you must not violate that license, and with that the WMF can send DMCA C&Ds.
Since Enterprise does have API keys, it in fact gives WMF control over exploitation of it enforceable in the way you mention. Enterprise is what defends our copyright.