They injected miners in websites and even free CI pipelines on GitHub and similar.

Presumably, "nazi" here is a stand-in for any form of communication not protected by free speech laws and / or is actively forbidden by government censors (or perhaps merely undesirable by social standards). Hate speech, anti-government advocacy, promotion of violence and terrorism etc will use "free" tier accounts because they want as little capability of being tracked to in-real-life people as possible.

They may or may not fully utilize the bandwidth, but they will absolutely take advantage of access to resources that don't require real identification, and that adds an extra burden of regulatory compliance on the company offering it (even if it is just hiring a few extra people to manage takedown orders, etc).