More like WhatsApp used Signal's protocol. The Signal Protocol was in existence before WhatsApp started using it. It uses that protocol because of the fact that it's the gold standard of end-to-end encryption protocols. Telegram's protocol was criticized because it was vulnerable in various ways that Signal's protocol was not. Encryption experts cross the world pretty much universally agreed on that. The reason why governments don't go after Signal, but they went after Telegram, is because Telegram didn't encrypt all that much. In fact, it only encrypted things if you specifically told it to. There'd be no reason for governments to even try to go after Signal if everything's encrypted and that nothing can actually be taken from it. In fact, governments have tried to get data from Signal, but were unable to take anything because of how everything is encrypted except for basic data like when a person first started using the platform. It's ironic that you're talking about all of this while supporting SimpleX, which is backed by a for-profit corporation and is relatively new to the field, thus meaning that they have not been proven quite like Signal has been. By all means, SimpleX is a very neat tool that I am very much looking forward to seeing the future of, but if you want security, you really can't get better than Signal. This isn't just my opinion either. This is the opinion of virtually every security expert, cypherpunk, etc. Edward Snowden himself recommended it, and if someone with such a high threat model is confident in using it, then average Joe on Nostr can use it.