Why is the wrong website opening for me?

Question

Nginx

I have 2 websites backend and frontend. Both should open separately, but for some reason my backend pages open the same way. The fact that admin.rsi.local.
How I configured nginx
/etc/nginx/sites-enabled/rsi.local

server {
        charset utf-8;
        client_max_body_size 128M;

        listen 80;

        root /home/ruslan/Development/rsi/frontend/web;
        index index.php;

        server_name rsi.local;

        access_log /home/ruslan/Development/rsi/vagrant/nginx/log/frontend-access.log;
        error_log /home/ruslan/Development/rsi/vagrant/nginx/log/frontend-error.log;

        location / {
                try_files $uri $uri/ /index.php?$args;
        }

        location ~ \.php$ {
                include snippets/fastcgi-php.conf;
                fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
        }
}

/etc/nginx/sites-enabled/admin.rsi.local

server {
        charset utf-8;
        client_max_body_size 128M;

        listen 80;

        root /home/ruslan/Development/rsi/backend/web;
        index index.php;

        server_name rsi.local;

        access_log /home/ruslan/Development/rsi/vagrant/nginx/log/backend-access.log;
        error_log /home/ruslan/Development/rsi/vagrant/nginx/log/backend-error.log;

        location / {
                try_files $uri $uri/ /index.php?$args;
        }

        location ~ \.php$ {
                include snippets/fastcgi-php.conf;
                fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
        }
}

And in /etc/hosts

127.0.0.1       rsi.local
127.0.0.1       admin.rsi.local

And reloaded nginx
sudo service nginx reload
And it seems that the front in rsi.local should work and the backend in admin.rsi.local should work. But everything works for me from admin.rsi.local even if the address is rsi.local.
Why is this happening. But if you remove it from sites-enabled/admin.rsi.local, then the site from the front works again

Answer 1

server_name must be different.