Falcon 9 was a more conservative rocket. The big new thing was recovering the booster, and there were lots of failures for that. The other big difference is tha

Falcon 9 was a more conservative rocket. The big new thing was recovering the booster, and there were lots of failures for that. The other big difference is that Falcon 9 uses the Merlin engine, which was developed on Falcon 1 rocket which had multiple failures. Starship is trying something new, recovering the second stage that goes in orbit. Which means bigger rocket and more complicated second stage. They are also using new Raptor engines. The last two failures have been new version of Starship, and they either broke something or haven't been able to fix problem.