react into frontpage fail

[1337180]

Hello,
Here are my steps:
npx create-react-app jreact
yarn build
now I have react starter app tested in localhost here is running fine with reactlogo text css everything
create new folder called react in joomla core folders tree on server
create folder static
create folder js/css/media within static and put there libralies
I was calling js files with css files from mainpage and from index.php in cassiopeia
nothing happened, cant see anything
thanks for help

[1337180]

I forgot div root. Such a stupid mistake, I am sorry.