Dude - I’m sorry to hear that. I’m not part of the Anchor team, but here is how I understand the collateral works.
If you post $10k of bluna, the maximum you can borrow is $5k, but that means any kind of dip in bluna means you will get liquidated. You need to keep a minimum of 2x your loan value as collateral.
If you posted $20k bluna and borrowed $5k, that means you will get liquidated when your collateral is worth $10k, i.e. if luna drops 50%. MakerDAO has a similar overcollateralization requirement where you can only borrow up to 66% of the value of the collateral.
The safety margin is there because crypto can be very illiquid and volatile and the protocol needs to protect the depositors from losing money. If they started liquidation only once the collateral value equals the loan, then the depositors are almost guaranteed to lose money.