I'm in a hurry, so I will only answer only briefly: In global history circles there is this debate going around a phenomenon called the "Great Divergence". Why did some parts of the world become rich while other stagnated. There are several schools of thought regarding this issue, the newest one, the California School, working with the assumption, that the world was fairly equal in terms of wealth and economic development right up until the industrial revolution.

There are also some problems in how you seem to think about this question: What do you mean by laggin behind? History is not a video game, progress is neither linear, not inevitable. Japan was also never completely isolated. Through dejima and the Dutch, they were connected to the rest of the world.

I was lucky enough to have Peer Vries as a professor, and I cannot recommend him enough. If you are truly interested in this topic, read Peer Vries, Escaping poverty. The origins of modern economic growth, 2013.