Because Evergreen is the name of the company that operates the ship [1] and Ever Given is the name of the ship [2].

[1]https://en.wikipedia.org/wiki/Evergreen_Marine

[2]https://en.wikipedia.org/wiki/Ever_Given

Evergreen is the company name, Ever Given (which does appear on the ship in much smaller letters) is the ship's name.

The name of the company is Evergreen. All their ships start with Ever. This ship is Evergiven.

"Ever Grounded"?

Evergreen is the company, all their ships are named "Ever X" where "X" is some word that begins with "G".

Like how some people name all their kids with the same first letter. I know, weird.

This confused me, too, at first.

The vessel name (on the bow) is Ever Given.

The company operating it, emblazoned on the side in large letters, is Evergreen.

Evergreen is the company, Evergiven is the name of the ship.

Evergreen Marine Corporation owns the ship named Ever Given.