That sentence just says why we're making a national government (i.e. giving up some of our rights). It does not create some unlimited requirement for governments (especially state) to do whatever they can to promote general welfare, whatever that means. It doesn't even grant unlimited authority to do so. Or really say anything at all except state a very general purpose for why a national government is a sensible thing to have.
> We the People... in order to... [do establish] this Constitution
> We the People... in order to... [do establish] this Constitution