Mass printing brings literacy to the masses, more ideas get written down and shared, more breakthroughs spread instead of dying with their inventors, stronger bureaucracy with more efficient methods of governing encouraged by the Senate/Emperors as a result of power struggles leads to the nation holding together much better in the long term, providing the long term stability of a large market with relatively easy transit via the Mediterranean and the Roman road system leading to competition between producers for more efficient methods to make their goods, which over the course of a few centuries leads to widespread adoption of things like heavy plows, crop rotation, water wheel powered factories and machines, and then after a couple centuries some bright young son of a senator with more money then sense digs up some old references to a steam powered machine built by an ancient thinker, decides for whatever reason he can do it better (see more money then sense) and using the best metals he can get his hands on actually creates a working model, which although horribly inefficient quickly becomes popular in coal mines in Britannia and Germania, and from there they just get better and are used in more situations until one day, the entire society seems to run on steam or electricity produced by it.