The "Dark Side" ending (killing Vader) for TFU1 was the non-canon ending, in the post game you hunt down and kill old Obi-Wan and turn Luke to the Dark Side.
Well this has two points.
1. Natural force affinity. Some people have much higher affinity than others, and brute force can overpower skill, especially when...
2. He was caught by surprise. He had no idea Rey would be sensitive nor did he have any inkling of her natural power, so of course she...
Yes, a person who spent their life fending for themselves and scrounging shipwrecks would have no idea how to handle themselves in a flight or fix a ship or know how to fly that's so unbelievable.
Also, yes, Force Ex Machina. It always has been a completely silly plot justification but the...