They're just showing their dedication to transparency.
That reminds me of my first N26 bank card in Germany. I got one in the mail and immediately called them: "Wtf? Why is the card transparent?". 5 seconds later: "That shows our commitment to transparency..."
RobinHood's bank card is half-transparent, half-full-black. I wonder what they're trying to tell us?
so when another class is added that makes the element have opacity: 1, it animations a transitions from 0 to 1