Completing the registration processes and uploading the product details correctly on the platforms in not a battle half won, it has just begun, to be honest.
Running an online business on marketplaces is a full time job – for one person or more depending upon the product range that you carry.
For businesses selling on only one platform, managing inventory is relatively easy vis-a-vis someone who is selling on multiple platforms. Businesses going online for the first time will find it even more difficult.
And this is not limited to inventory alone – a seller also has to make sure that the final selling price of their products after all discounts and offers does not have much variance across the multiple platforms that they are selling on.