Perhaps it was a rushed tradeshow/employee perk gone awry. Something like:

Tradeshow coming up very quickly, previous merch supplier has let the sales team down.

Mid-level Haribo employee responsible for merch finds a supplier willing to rush through everything, because let's face it, Haribo are probably going to pay their bills.

MoQ is 100 units, which is 1 lot.

Sales person intends to order 2000 units, better to be safe than sorry and run out. Accidentally orders 2000 lots of units with 100 units per lot. This isn't noticed until they're already printed and then it's, as they say in the legal profession, no takesie backsies.

Haribo suddenly have a lot more power banks than they have booth visitors, and employees combined.

Rather than store them indefinitely, they sell them off at cost and shift them quickly though Amazon. This drastically cuts down on warehousing space of small lithium (explosive) packs that the candy people have to store.

And kids and grown-ups love it so, with 20,000mAh wherever they go.