The Guardian in another article explains that they are annoyed because Musk used twitter to promote his preferred candidate.
The Guardian itself used their own platform to publicly endorse Harris.
This deja-vu of childish antics is just comical in 2024
The Guardian is a newspaper. They broadly have two sections: reporting and editorial. Reporting is basically that. Now you can (correctly) argue that there is bias on the reporting side in how they choose to cover certain stories, how they choose what stories to cover, etc but there are still minimum standards they adhere to, like they won't knowingly print anything objectively false. They'll issue corrections and retractions if necessary.
The editorial side is quite literally opinion. The Guardian, like any publication, can issue their opinion on a given political race. But you know that's opinion. They'll argue why for their position. You can agree or disagree with their reasoning or conclusions. But it's intellectually honest.
Now compare that to Elon and Twitter. It's not even remotely the same. Twitter has an algorithm to decide what to show people. He's used it to push his own posts [1]. His own posts have openly pushed conspiracy theories [2], things that are provably false. This can go as far as pushing literal Nazi conspiracy theories (aka the Great Replacement [3]) and make sure as many people as possible see it.
It is utterly disingenuous to conflate the two.
[1]: https://www.theverge.com/2023/2/14/23600358/elon-musk-tweets...
[2]: https://www.vox.com/technology/2023/5/20/23730607/elon-musk-...
[3]: https://www.rollingstone.com/culture/culture-news/elon-musk-...