God says in the Qur’an...
And proclaim the hajj to people: they shall come to you on foot and on lean camels coming from distant places. (Qur’an 22:26-27) Islam, the perennial religion practised by all prophets from Adam to Muhammad, was present in all times and all places because it was meant for all people. For God, the eternal and omnipresent Creator, created mankind and He alone knows best how to guide them - sending prophets to every people, at all points of human history.
Man for his part, in his imperfect and fallen state, is always in need of God’s guidance and is the perfect receptacle of this Divine guidance and grace. But man in his fallen and earthly nature can not immediately conceive of Divine realities, whether it be this supreme guidance or man’s own essence and spirit. He needs help and support from the outside, so to speak. He needs tangible things to aid him and guide him towards guidance and the Guide.
The Ka’bah serves as this external symbol and is God’s House not because God needs a house, but because man in his weakness needs a solid point of reference to turn to. The Ka’bah is as a lighthouse which guides sailors lost at sea back to the shore and back to their home and origin. The first verse quoted above speaks to this role of the House of God being a source of guidance for all nations and peoples.
But it also mentions the House being “blessed”; meaning that there is really and truly grace flowing from this place and that it is a point that has been providentially chosen to be an “opening” up to the heavens. In addition to being for all people a source of guidance, the House of God - and the symbol of Islam - is also a refuge and sanctuary for people.