"Killing" is a pretty funny word to use.
Everything is easy when you're small. Look at Simple in the US; they have an awesome iOS app, a few interesting features, they gained customers, became more popular, and... feature development stopped. Their pace of externally-facing innovation has DRAMATICALLY slowed over the past three years. They've done automated expense allocating w/ recurring goals, family accounts, and protected savings accounts with a high interest rate, and that's, like, it. In three years. They don't even have 2FA w/o SMS.
Why is that? I don't know. But I have a suspicion: Banking is fucking difficult. Its insane. There's regulation and red tape everywhere, you make one mistake and you instantly not only lose customers but could ruin their lives. Its fundamentally not an easy industry to operate in. So, they have to allocate a ton of engineering effort into the back-office side of things, which is exactly what every other bank does. Simple even contracts with BBVA to handle the accounts, which should make some things easier.
Crypto doesn't change anything at all. Again, its easy and awesome when its small, and Crypto also has an advantage that regulation has been slow to catch up, so in some ways they can just shrug their shoulders and say "its not real money, you can't have the same expectations." For now. As it gets bigger it'll become subject to the same regulations that fiat is subject to, and years later it'll look exactly the same. The underground networks, including Bitcoin, can maybe escape some of this due to the lack of centralized corporate backing, but Facebook can't.