@saredesu
anime adaption is an advertisement to make more money from the original manga/novel and also merchandising. Most mangaka are very happy to have their works adapted because it enables them to reach a much wider audience and in turn it will almost always boost up the popularity of the manga.
Also Jump adaption=better adaption isn't always true. Look at some anime like Bleach, Naruto or Wan piss that go on for hundreds and hundreds of episodes and look like they're produced entirely by chinese sweatshop animators except for a few well animated episodes that are obviously the exception. Especially OP is probably the best example for an anime that only exists to sell merchandise and the manga, it's just so bad and ugly I don't understand how someone could watch it. and then even watch fucking 700 episodes of it.
Other shows like Kimetsu no Yaiba had a very good production and the adaption massively BOOSTED the manga. The manga started in 2016 and barely anyone knew of it until it got adapted and then it exploded in popularity.
And Watamote anime managed to reel in more readers and they changed the tone of the manga and it hooked the readers. If it wasn't for the anime, I'm pretty sure Watamote would already be long finished.
It's not like you can do a lot wrong with story/ending in a SoL manga like this.