Likely the hardest part of establishing a space-faring kingdom is going to be getting ourselves off the ground...

1) Because of physics - the cost of fueling enough trips to get construction equipment into orbit and also, you know, air and stuff.  The Falcon Heavy puts about 64 tonnes into orbit for a 'mere' $90M and, though the fuel is not a big chunk of the cost, using such large quantities is going to put a fair bit of pressure on both the supply lines and the atmosphere.

2) Because of people - nation states, political jousting and commercialisation have created a sociopolitical situation where characteristics of greed, envy, sneakiness, hard-nosed negotiation and selfishness thrive.  Choices like these feed and develop the machinery that generates and inspires more of the same.

This is, of course, not a description of humanity, nor do I think it is human nature.

My point here is that both of these things need to be tackled in order to make something that is truly new. Any technological solutions must be built on social principles of cooperation, coordination, compromise and charity.  Likewise, the social environment in which technology is developed must reflect these ambitions.

Commons that once brought only tragedy may now bear fruit.