I'm curious about what Elon means by the hypersonic grid fins running out of hydraulic fluid? It is a closed system, is it not? How can it 'run out'?
Also, so, as speculated on here, it sounds like the issue was more related to the final burn than steering. Either way, it seems like the chance of success was significantly more 50%
Sometimes rocket designers use an open loop hydraulic system, it's lighter and cheaper to carry a few minutes worth of hydraulic fluid and dump it overboard once it's passed through the actuator than include the plumbing to recycle back up to the reservoir. Unfortunately, it does make that system a limited resource for the flight, and if you have an actuator that seeks back and forth more than expected, you may drain the system faster than intended. Conestoga had the same thing happen on one of their test flights in the 90s.