Not necessarily so, but generally internet users pay very little attention to online security, and when it comes to smartphones that percentage is even lower. I can't claim that the OP would have been saved if it had AV/anti-malware, but it's certainly not enough to have an updated OS. From some past cases, I know that the iOS blockchain app was marked as something that many were hacked for.

---

I only use my home wi-fi network which is maximally protected, but I agree with you that it is still a risk. It would be best to use a wired connection, and it's not exactly an option on a smartphone, although it's feasible via an additional adapter.