"Astronomers have discovered the seemingly impossible. Using the powerful James Webb Space Telescope, they have observed massive candidate galaxies at the beginning of time, up to 100 billion times the mass of the Sun which, if confirmed, would contain more mass than was thought to exist in the whole Universe at that time"
Discussion
The James Webb telescope brings us new wonders every day 🌌
Why do they still assume there was a beginning to the universe?
i don't think most assume there is a beginning but it is easier to often talk about time as earlier time and later time and at some point in the far earliest times there was most likely a material event that materialized a universe that we experience.
but your question is good because before that event there was also something else