I am wondering whether there will be any further light shed on what provided the performance gains in MongoDB 8.0. How did they achieve these improvements? And I presume these are performance gains against MongoDB 7.x?

Has anyone else tried to replicate their claims?

I did a quick test and on my use case the performance improves mainly on a complex aggregation pipeline. I still have to run extensive benchmarks. I think one of the improvements is the New Query Engine: https://laplab.me/posts/inside-new-query-engine-of-mongodb/