President-elect Donald Trump measures people’s worth by ratings. (Jabin Botsford/The Washington Post)

On Friday morning, President-elect Donald Trump tweeted.

The first one went like this: “Wow, the ratings are in and Arnold Schwarzenegger got ‘swamped’ (or destroyed) by comparison to the ratings machine, DJT. So much for . . .”

It was quickly followed by this: “being a movie star-and that was season 1 compared to season 14. Now compare him to my season 1. But who cares, he supported Kasich & Hillary.”

The reaction was utterly predictable. Democrats — and even some Republicans — wondered why Trump was fixated on the ratings for “The Celebrity Apprentice” on the day that he was set to receive a briefing from intelligence officials about the depth and breadth of Russian hacking during the 2016 election. It was the height of irresponsibility, they tweeted!

Here’s the thing: We know — or should know — by now that this is a feature, not a glitch, of Trump’s personality. In fact, the tweets above provide a nice window into understanding how he thinks about himself, his looming presidency and the world.

For Trump, it is all about eyeballs. Attention. Buzz. Chatter. Appearances.

During the campaign, the metric that Trump kept coming back to was that he had the biggest crowds of any candidate.

“We go to Oklahoma, we have 25,000 people,” he said in August. “We had 21,000 people in Dallas, we had 35,000 people in Mobile, Alabama. We get these massive crowds. Look, if [Hillary Clinton] had 500 people, I would be surprised.”

In October, he sounded the same note: “No matter where we go, we have these massive crowds. We just left one that was 11,000 . . . It’s been amazing, the receptivity. There’s never been anything like this in this country.”

And again just days ago, he tweeted: “Hillary and the Dems were never going to beat the PASSION of my voters. They saw what was happening in the last two weeks before the . . .”

Ditto Trump’s views on the importance of TV ratings. He uses ratings as scientific proof of his immense relevance — in debates, on “Saturday Night Live,” at “WrestleMania” and, well, pretty much everywhere else. Ratings — bad ones — also serve as his go-to put-down tool. Everyone from Megyn Kelly to MSNBC to “The View” to Arsenio Hall has been judged by Trump as bad/stupid because of allegedly poor ratings. (The Trump Twitter Archive is invaluable for this sort of searching.) As Jacob Brogan put it in a Slate piece last year:

“Trump cares about ratings a lot. He cares about ratings because the value of a thing, in his mind, is entirely a function of its ordinal positioning. He’s always talking numbers, one way or another. During one recent campaign stop, he counted up every reference that Hillary Clinton made to him in her Democratic National Convention address — 22 in all. He also routinely talks polling data — mostly when the numbers are in his favor, but sometimes even when they’re not.”

Yup. Ratings make the man. If people watch, you win.

Trump’s focus on the appearance of things carries over to how he has gone about picking his Cabinet. This, from a hugely insightful Washington Post story published late last year: “Donald Trump believes that those who aspire to the most visible spots in his administration should not just be able to do the job, but also look the part . . . Given Trump’s own background as a master brander and showman who ran beauty pageants as a sideline, it was probably inevitable that he would be looking beyond their résumés for a certain aesthetic in his supporting players.”

Remember that Trump — like all of us — is a product of his environment. That environment for him is the meat grinder of New York City business and media — and, more recently, reality TV. How you come off in those venues often matters far more than what you say. The key is not, necessarily, to be the smartest or the best looking; it’s to be the one everyone is talking about. If you are the center of attention, you’ve won. Nothing else matters. Crowds, ratings — that’s the measure of a man.

No one should be shocked that this “appearances first, second and only” view is coming with Trump as he prepares to become the 44th man to be U.S. president. At 70, this is who he is. He has spent a lifetime measuring his success through numbers — not always correct numbers, mind you, but numbers nonetheless. Perception is Trump’s reality. In that way, he is perfect for our modern political system. And he knows it.