From Priceonomics which notes:
In our sample of Times pieces, we only found one chart used outside the Business section before 1990….By the late 2000s, charts had become central to the journalism at the Times. The newspaper had a team of graphics reporters infusing the paper with innovative visualizations. For the Times web edition, those data visualizations were often interactive.
…The New York Times cemented their prioritization of visual journalism when they launched the data-driven news site the Upshot in 2014. The Upshot’s original team of fifteen included three full-time graphic journalists.
Computers are the obvious driving factor. Data analysis and visualization are powerful tools. I would guess that data IQ has been increasing ala the Flynn effect.