setting innerHTML is not working sometimes [duplicate]

This question already has an answer here:

• How to change the Content of a <textarea> with Javascript 5 answers

im trying to set the inner html of a textarea via a console command this is what im using:

document.getElementsByTagName("textarea")[0].innerHTML="test";

in the inspector i can see its changing but in the body of the page i can see its not. only after i manually set the innerHTML of the textarea via inspector i can can do it via a command

it doesnt work before manually doing it. why is it doing this?

ive tried other stackoverflow posts but they dont work either