Mars Finance News, Solana Foundation Strategy Director Austin Federa published an article on the on the roadmap.
The main reason was probably that we didn't expect demand for Solana to increase so quickly, and within a few days the question went from "adequate but needs improvement" to "deficient." Austin Federa concluded that the problem is simply technical debt, and that the network stack will be almost completely rewritten later this year, while at the same time weighing important maintenance/improvement work.