Granted the Vasudans are aliens but I can't actually say Petrarch was wrong per se or anything, if Vasudans feel jealousy as humans do. It was just very undiplomatic. Granted, the Vasudans do have a focal point in the Emperor, which the Terrans apparently don't (culturally at least, legally they do and they have very good defense reasons to bind together).
That said, you can't discount economics either. It's one of the key responsibilities of government and if the Terran Knossos was such a large budgetary drain, it used up money that could have used it to stimulate the economy after Capella (fiscal policy) and encourage growth (infrastructure, subsidizing colony reclamation and settlement). You could probably see the effects of that in less than 18 years and the risk involved in financial terms is much lower than going back to Earth, which have been anywhere at from extreme (decimated planets that suffered badly from the socio-economic changes from node collapse to the jewel it is now).