Probably bundling the server side dependencies into the client. I’ve also seen this happen when people add uncompressed 4k png images and the build tool is configured to inline all static assets. Obviously there was a lack of domain knowledge in the company or this wouldn’t have happened.

What I understood from the post was that it was only 168mb because tree-shaking didn't work on whatever version had support for server-side rendering. With working tree-shaking the bundle these developers were working with during development would be considerably smaller.

Wouldn’t be at all surprised if no one was paying attention. Chrome on a top spec MacBook can chew through 100MB of JS without thinking about it. Someone on an old machine is screwed but hey, “works on my machine”…