The real question is why did they want this? Is the UK suffering some giant crime wave or are the powers that be just really intent on making sure people are using Bad Think in their private chats?
The basic premise is that online platforms like Facebook and X will have more legal responsibility and requirements to follow particular UK law and guidance on content that their platforms host.
This is very popular with the press and enjoys widespread public support in polling. All major political parties support it.
The encryption and scanning aspects of it are just one part of the bill.