In order to accomplish your goal, you will need to employ two transformations.
First, split your Column B into separate columns, as many as the row that has the most values. Then, use the Shape : Depivot capability to generate rows for those values.
Select the menu option:
Input the correct separator ", " and accept Paxata's automatic insight on the number of columns to create:
In Depivot, choose columns that stay put and repeat for every row created, then click REST to make the new columns create rows: