Ask HN: Why did Bill Gates stop tweeting?

Just to clarify, he donates hundreds of millions in the aggregate, not to each outlet.

Reading your link,

    I recently examined nearly twenty thousand charitable grants the Gates Foundation had made through the end of June and found more than $250 million going toward journalism.

    [ ... ] For example, in 2015 Gates gave $383,000 to the Poynter Institute, [ ... ]

and noting that it was written in 2020 and discusses examples from 2015 it appears that the Gates foundation donates at most $50 million / annum (perhaps less) to a broad range of media outlets across numerous countries.

The 'complaint' isn't specific to the Gates Foundation:

    And that speaks to a larger trend—and ethical issue—with billionaire philanthropists’ bankrolling the news.

    The Broad Foundation, whose philanthropic agenda includes promoting charter schools, at one point funded part of the LA Times’ reporting on education.

    Charles Koch has made charitable donations to journalistic institutions such as the Poynter Institute, as well as to news organizations such as the Daily Caller News Foundation, that support his conservative politics.

    And the Rockefeller Foundation ...

For balance it's relatively easy to make a case that the combined Koch donations to think tanks and news outlets since the 1970s have been far far worse by magnitudes for humanity in toto than anything yet revealed about the Gates foundation.

The Koch brothers very nearly singlehandedly tanked public transport in the US and delayed action on non fossil fuel climate technology for four to five decades while encouraging greater and greater excessive use of carbon based fuels.