When the EVSE blinks the power light, it's letting you know that it cannot find a valid ground path. This is a built-in safety check, and without this test being passed, the EVSE will refuse to allow charging.
Since with a generator, there is no true "ground" as referenced by the earth, unless you drive a copper ground rod and properly bond it. The high-value resistors provide a balanced middle ground which will still safely pass small amounts of static and RF signals back to the body of the Leaf where they should be without providing a hazard where by a fault could cause deadly current to be available on the body of the Leaf and/or the Generator. The 100k resistors will not allow enough current to pass to present an electrocution danger to anyone, and it splits the difference so the maximum possible voltage potential over the floating ground is only about 60 volts at any time.
This is safe while still satisfying the EVSE's ground verification test.
Doing a hard bond without the resistors would now FORCE the body of the Leaf and the generator to be hard-connected to one side of the AC line, so in the event of a fault or alternate path, it could pass lethal electrocution current into a person. Keep in mind without driving the ground rod there is no effective neutral, as there is no reference to ground. Both power lines are effectively floating until you make a bond. This is known as "isolated ground" and would be fine, except the EVSE will not approve, and it also presents a hazard of damage to any of the connected systems by static and/or RF energy build up with respect to ground. If the static charge builds up and jumps into a nearby conductor, this sudden current could damage a component, such as the multi-kilobuck on-board charger module in the Leaf, the EVSE, or one of the generators system, such as it's automatic voltage regulator.