The "sweat of the brow" argument is not valid in the US.
This person isn't just collecting existing letter shapes; inventing a new letter shapes would be protected by copyright?
There are lots of things that can't be copyrighted.
For example you can't copyright an anatomy drawing: https://www.skeletaldrawing.com/licensing (i.e. the layout of the bones, etc) but you can copyright your specific drawing - but someone else could draw in the same style and not violate your copyright.
Same here: You can't copyright the shape of the letters, but you can copyright you specific ttf program (expression), but someone else can make the same letter shapes if they want.
There are many ways to draw the same letter, as there are many ways to draw a cat.
Also if one draws letters that look like cats, will they fall under copyright protection?
You need something "extra", some kind of style that is distinct.
I'm not saying your drawing has no copyright - it does, if someone reproduces it exactly that's illegal. I'm saying if someone makes the same type of drawing, in the same style, that's not infringement - even if they looked at yours, as long as they drew it themselves.
It is settled law that letter shapes aren't copyrightable. Period.