Not sure what you call the part that holds the ball bearing on the lower stem but that needs to be removed before you put on the thing washer, gasket then tapered bearings.
It is called the inner race. Yes it needed to be removed.
At 7:04 seconds on the video you made the 2nd mistake that caused the problem.
That thick washer had to go on the triple tree first. Not that thin washer.
It has to have the thicker washer on first. It makes the clearance so the triple tree does not rub the fork stop on the bottom of the frame headstock.
You will have to take it apart.
Use a brass punch on the bearing races .DO NOT pound on the race with a screw driver blade or any steel tool. It will deform the race.
One more thing. The way to put the grease in the bearing..... Put the grease in the palm of your hand like you did but then hold the bearing on one side with the small end sticking up.
Then make a downward stroking motion on the grease forcing the grease upwards through the bearing until you see the grease push out the top of the bearing.
All you have to do is take it apart and carefully, tap the bottom race off and then put that thick steel washer on the bottom first.