What happens to the Infanta (great jobs, good salaries) happens to almost all royal children in reigning monarchies. It comes with the package of belonging to a family in the top of the social pyramid.
Doña Cristina already lived a luxury lifestyle before Urdangarín became an executive of NOOS, so the big house and big lifestyle was not connected to NOOS per sé.
I agree with you - usually 'golden jobs' are given to family members by friends and connections, eg the job Cristina currently holds, provided by the Aga Khan. Elena's husband Jaime held a similar job during the marriage.
Inaki is different, because he was too arrogant and stupid to accept such a job (he turned down a 200.000 Euro per year job at Laureus because he felt it it was not good enough), he wanted to provide all the luxury life by himself, so he started doing shady deals involving public money because of his status, son in law of the King, and the 'business' went well. He funded the extra-luxurious lifestyle on stealing public money (JC even recommended him). Yes, Cristina is a rich woman (she'll become really weathly when her parents pass away), but Inaki wanted more, he wanted to show off what he created, what a great business guy he was and his wife looked the other way. People already started asking questions when they bought and renovated the Pedralbes house, way over the top for Inaki.
In the end the King had to force Inaki to take a 'golden job', Telefonica in Washington, to get him out of the way, but it was already too late, because the economic situation was turning to the worse and the King thought it was a good idea to shoot an elephant in Africa, both incidents made public opinion change and people taking a closer look to the dealings of the SRF. Cristina became a scapegoat because she did not want to do what the public relation department asked her to do, back down and be quiet.
You are right lula, no RF is white and clean, but over the years people could witness some difference of behaviour with all family members, when in public and in private, what leads to the thought that they are all hypocrites:
Juan Carlos: travelling to Africa with his mistress and shooting an elephant, nobody would have known had he not broken his hip, in times of economic hardship
Sofia: travelling to Washington and posing with Inaki, who was already accused of stealing public money, for pictures, smiling, after the scandal broke, in times of economic hardship
Felipe: not doing anything about it for years, still posing smiling with Inaki on his birthday shortly before the scandal became public
Letizia: not in connection with Cristina and Inaki but her yoga friend, involved in a credit card scandal, labelling the magazines writing about it as 'sh*t', assuring her friendship, 'to hell with the rest', meaning everybody outside their circle = the public.