The problem with alot of gift cards is that they often don't have functions in place to prevent someone from brute force attempting the PIN code. So if they can figure out the sequence of numbers for the card, and then just try thousands and thousands of combos for the PIN code, they can move the funds off that way. Companies that let you register the card offer some form of protection against this (the amount varies by the companies terms), but that isn't always perfect.
RE
Disney+, Disney wasn't hacked. People had re-used passwords across multiple sites. So they registered for Yahoo using
SallyLovesDisney@gmail.com and the password of MickeyRocks, and then used that same email/password combination for their Disney+ registration. Millions of passwords for Yahoo accounts were stolen over the years, and plenty of people don't change their password. It's like using the same PIN for your ATM card and your luggage lock. So some bored people took that info from the Yahoo breach, and plugged em in to try to log into Disney+ and found some that worked.
Check out
https://haveibeenpwned.com/ to see if an account/email you used has been compromised. It's not 100%, but you may be surprised at how many places have been hacked and didn't notify you. I believe the new Lockwise account storage in Firefox will show you similar data based on the sites you have stored locally.