That is so great you decided to buy them, poor things.
What are betta fish? Are they like Siamese fighting fish? That is terrible to put two together, I think taco will survive and is obviously very grateful for his lovely new home. I suppose it could've been done by somebody who wasn't aware you can't put two fighters in the same tank?

We recently lost two of our tetra's to swimbladder, tried everything but didn't survive.

I think Taco is lovely