I don't agree with all this and this increasingly fascist regime but... this was the most predictable outcome. Consider these two scenarios.
1. You factory reset your phone before entering the US and give it to CBP blank. There's nothing to find;
2. You have a self-destruct PIN like this guy did and give it CBP so it destroys the phone's contents.
Tech people will say that these two things are functionally the same. This is a fundamental misunderstanding of how the law works. If you factory reset your phone first with the intention of restoring it after entry, that's completely fine (legally). You could've factory reset that for any reason. But as soon as an officer wants to search your phone, now you're engaging in evidence destruction (spoliation). The destruction to the phone's contents was done in response to an unfortunately lawful search.
Even if you don't want to factory reset your phone, you can probably just delete (or even log out) of key apps. They can still get messages but if you're so concerned about that, use WhatsApp or whatever.
None of this should be necessary but we are where we are. But whatever you do, don't use a self-destruct PIN if you don't want to be charged with a felon and likely to be found guilty.