How to connect database without affecting the front end of a webpage?

Question

I have successfully connected the front end of my web page to my database, allowing me to retrieve the necessary information. However, this has drastically changed the front end of my website for some strange reason. I have used mainly Typescript throughout this project.

Its a react app using vite to load the frontend and backend using node.js with express.

I urgently need technical help with this to get my waitlist launched.