The Ming dynasty (late 1300 - mid 1600 ish) started well but for very unclear and contentious reasons ended ship based trade (famously burning records and ships - including ones that may or may not - probably not - reached America). They did turn inwards - but that was fairly fine - China at 1400 was at the technological peak, life was pretty good for the average peasant, frankly it was about as good as it ever got before industrialisation.

Like the T-Shirt says, when you are this good, why try harder.

The most advanced civilisation on the planet simply sat back in 1400, and no-one could do anything about it because the place was one fairly unified political system.

(yes, wars rebellions etc, but one China - maybe broken at times but always seeing itself as one, not competing to beat the other part but competing to unify again.

Probably it's fair to say that China always fought itself, and Europe fought each other.

(There is also something about how China unified and grew in waves related to the latest horse invaders. A sort of unified and strong when the invaders attacked, weaker when the threat retreated. Once gunpowder was invented that process was effectively over - you could mow down horse archers happily all day. So again, China had no external threats so it could turn inwards. And take all of this as a massive over-simplification but it's interesting to realise the end of the horse invaders coincided with gunpowder and the turning inwards)