Is Terra Luna a ponzi scheme or a fantastic Bitcoin backed bank?

I’ve been using Terra lately loving the stable coin returns and swift price action of the native token. I’ve heard some accusations it’s a Ponzi scheme and I realized I don’t actually understand where the Anchor yields are coming from.(?)

I also heard Terra Labs is looking to buy 10 billion dollars of bitcoin. This seems like the smartest idea ever to back stable coins with bitcoin. That also got me wondering how/where is Terra getting 10 billion dollar to buy bitcoin?

How can I better understand and find out if Terra can sustain all this or if it’s a Ponzi scheme? Seems like if Terra’s model is sustainable and regulators allow them to do their thing with stable coins, they are the most important useful/valuable blockchain network below bitcoin. It could be the bridge between bitcoin and fiat.

Someone please help me understand and hopefully give reassurance. Cheers!