Saudi Arabia banked funds more effectively - they have the fifth and twelfth largest sovereign wealth funds in the world. Venezuela has roughly .1% of that, for the same population.
Beyond that, Saudi Arabia has substantial infrastructure development to pull oil out of low-value land. Venezuela has ongoing fights over which reserves should be recovered (it's under valuable rainforest and watersheds) and excess spending has steadily undermined infrastructure - their break-even price is ~15% higher than Saudi Arabia's.
So: Venezuela sank their wealth into some mix of corruption and admirable initiatives that nevertheless haven't paid themselves back. Saudi Arabia saved the money and drove down production costs.
Saudi oil is also much easier to pump out of the ground and refine, even if you discount infrastructure investments. Venezuela oil is notorious for being the opposite (not their fault, this is just a curse of geology).
Our general idea of how life is for a Saudi is lacking, sources suggest a 25% poverty rate^ in the country. They execute protesters and journalists covering the poverty issue, and have been trying to shift attention away with war in Yemen.
Beyond that, Saudi Arabia has substantial infrastructure development to pull oil out of low-value land. Venezuela has ongoing fights over which reserves should be recovered (it's under valuable rainforest and watersheds) and excess spending has steadily undermined infrastructure - their break-even price is ~15% higher than Saudi Arabia's.
So: Venezuela sank their wealth into some mix of corruption and admirable initiatives that nevertheless haven't paid themselves back. Saudi Arabia saved the money and drove down production costs.