On the topic of inventory. The Anker product line is so wide and diverse I doubt they make them all continuously. No they're likely making a few products at a time in large batches based on popularity. I'd expect a 6-8 week lag between seeing need for products and it being in stock in country (manufacturing, export, import).
So if they don't have inventory you're having to wait weeks. Then they also have to respond to demand, so one product might never get made again if some other product is really popular. Then also products are eventually superceded so never available again.
Hence the competitions and discounts is a way to nuance inventory, if you made a big batch and in stock and not quite as popular as forecast you can shift them faster.
I suspect therefore in this case more Powercore II 20000 we're being bought in Amazon than expected so they had to change minds between creating competition and the final decisions. But this is Anker's internal business.
So best to see this as a stream of "now".
The other, not your point but same root cause, is technology aging sour grapes. The minute a product is made, it is aging, the successor is being designed. In other forums, people complain they just bought a new product and it's successor came out. Or they just bought it, but others are not buying as fast as forecast so a discount appears just after they bought.
All these are just logical consequences of supply chain.