Nginx Reverse Proxy working on wrong server_name (Sub domain ignored)

I have a created new Nginx server which I am using for reverse proxy for my 2 NodeJS apps.

1. First app I need to run on example.com
2. Second app I need to run on endpoint.example.com

I created the file endpoint.example.com in sites-available as follows, enabled it and nothing worked (default "Welcome to nginx page kept showing"). As soon as I remove the default file from sites-enabled, my endpoint app started working on example.com instead of the subdomain endpoint.example.com

My Nginx version is nginx/1.18.0 (Ubuntu)

I haven't even reached the second app and therefore, my sites-enabled folder has only one file which is endpoint.example.com

I don't understand what is happening, server_name is being ignored.

server {
    listen 80;

    server_name endpoint.example.com;

    root /var/www/html/endpoint;
    index index.html index.htm;

    location / {
        proxy_pass http://localhost:3001;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}

The default file (No longer active, deleted from sites-enabled):

# Default server configuration
#
server {
        listen 80 default_server;
        listen [::]:80 default_server;

        root /var/www/html;
        index index.html index.htm index.nginx-debian.html;

        server_name _;

        location / {
                try_files $uri $uri/ =404;
        }

}