The goal of the Exodus on one hand must be Sinai - to meet with God
Yet Sinai is only a stopover then they head to Canaan - so what's the deal?
Well if we take 'promised rest' to be defined as an 'enjoyable relationship'
then this may make sense
At Sinai - they are scared of God, and God shows His fury at them - what they need of course is a mediator and prophet - played by Moses
But it is this mediator also plays the role of priest - he must make the people acceptable to God
On one hand He offers gifts & sacrifices for them
but on the other - He must make the people acceptable (holy) to God
thus the wilderness is the process of the prophet/priest making the people holy to God - i.e. bringing them from a 'distanced' meeting with God into an 'enjoyable permanent relationship' with God
the process of stripping away and a different kind of feeding
so the goal is not only are they 'ready' to enter Canaan - but looking forward to a restful relationships with God - the desire of all that 'striving' (cf Heb 4)
the wilderness of course is risky and painful business - and it causes many to long to go back to being 'alone' suffering in Egypt - basically the desire for bachelorhood once again