Except it was Amazon that pulled the app from the Microsoft Store. So why would Amazon then hosts it back onto its own store which cost them their own bandwidth? It's a free app so Microsoft ain't getting a cut, so the smart thing would have leave it on the Microsoft Store and let Microsoft paid for the bandwidth.
Amazon just laid off 2000 people on their hardware division (which includes alexa).
https://www.theverge.com/2023/5/30/23742109/amazon-alexa-celebrity-voices-discontinued
Alexa doesn't make money. Cortana doesn't make money.
That's why they are gone. It is as simple as that.