Technological advances are not always even. France had a very large region of decent, arable land. Their land was settled, even if they had room for development. You mentioned Prussia, their land was unsettled backwater full of swamps and woods, and a western swathe covered in sparsely-inhabited hills. When you introduce new technology to allow land clearing and drainage it's going to help Prussia a lot more, again for the industrial revolution pulling people to their Ruhr area since it had the sweet coal mines. France already has its land cleared and populated; less room to grow.
Napoleon is also not to blame, no matter how dramatic his impact, since France was basically stagnant or behind others for centuries before him. If you look at their demographics using modern borders you see they basically recover from the black death and just hover around that amount. No way this can be blamed on one man's escapades in the early 19th century.
I blame France being ahead of the pack in the areas that matter. It's not that they failed so much as they got their first and then everyone else eventually caught up. They had their land cleared and accessible, others took time to make it suitable for settlement. They had their liberal revolution first (not counting special snowflake colonies) and were ahead of the pack on the liberties and freedoms that often led to ladies not wanting to pop out a dozen kids. The result was that nations like Britain and Prussia were seeing triple digit percent pop growth in a lifetime while France was "only" seeing a few dozen percent, during the industrial revolution. The french pop growth declined into stagnation (I think it sat at 8% for a while) while others were still enjoying it higher. Ironically, when the rest of the industrialized world (except snowflakes) started to see a massive downturn in babies and growth rate, France ended up becoming on the high growth rate side more recently.
