Have to say I'm massively anti-Trump but you're (and the author of the tweet) drawing totally wrong conclusions from that data. It runs until end of February, during which time Trump was still vying for the nomination in a rampantly toxic selection process. Clinton's was virtually a procession; so where do we expect the vast majority of the media coverage to be centred? Plus he was from outside of the political norms at that time, a hilarious novelty candidate as it were - as he should have remained.
Judging by the graphic style I suppose that's been used in the Economist - hardly going to get balanced Trump media therein.
Let's keep it honest