There are several factors. Firstly, Harry's role as the hero makes him a prime target for exploring the pressures of being in that position. In the books, we see glimpses of his busy life but fanfic writers want to expand on it. Secondly, it allows for a lot of creativity. Writers can come up with different ways the overworked Harry might react or change. It also gives a chance to show a more human side of Harry, with all his exhaustion and struggles, which might not have been fully explored in the original series.
Splendid was similar to resplendent, gorgeous, magnificent, wonderful, brilliant, glorious, gorgeous, bright, beautiful, rich, gorgeous, gorgeous, brilliant, and so on.
The synonymous words of great momentum were: great fanfare, magnificent mountains and rivers, all-powerful wind and clouds, swallowing mountains and rivers, vast seas, ten thousand horses galloping, magnificent, heroes achieving success, and majestic.
Another theme is self - sacrifice. Merlin often puts his own well - being aside because he's so overworked. He'll skip meals or sleep to ensure Arthur's safety or to deal with a magical emergency. In some fanfics, this leads to him getting sick or making mistakes that he has to fix later.