Well I think we English had a little hand in that, we did have a habit of taking over some of their colonies (New Amsterdam, Ceylon and Cape Town being the main examples) not to mention that the increase in English/British naval power and trade saw the Dutch lose out. The constant wars on the continent must have had an effect as well, the Dutch were constantly at war with Louis XIV from the 1670's to the 1710's.
With the Second World War they didn't do too bad given the circumstances. The underground resistance was quite effective, many went into exile and fought with the allied armies as well (I believe there is one regiment in the Dutch army today that wears British style full dress uniform to commemorate the fact that they were founded in exile in the UK).
