And you may say “that was after 8 years, Trump only had three!” but here’s Obama in the middle of his presidency, 2012.
The change had already started. His hair had noticeably grayed, the lines in his face had become significantly more pronounced, you can see the wear the presidency has taken on him. It’s not just Obama either. Check out this set of pictures of presidents before and after —
https://www.goodhousekeeping.com/life/career/g3918/presidents-before-and-after-office/?slide=20