I feel that the best thing is to avoid talking business to strangers on the internet because most of them most be scammers. Assuming Alex didn't listen to them and ignored their request, he wouldn't have fallen for the video call which he got affected from. I ignore messages or emails from strangers because in my country, you see random numbers sending text and emails from people you don't know. However, offline wallets are the best.
Can we really avoid strangers completely? It takes a day to know someone and then form a relationship with that person. Severally, people we don't know in person but must have seen our work online have reached out to us to either promote a brand or work on some project together. It is our duty to verify if those offers are genuine.
The only mistake I see that Alex did here was not verifying those scammers to ascertain if they are really business people. Alex had that amount of bitcoins but chose to store them in a hot wallet; a device he uses everyday. I consider Alex a victim of his own ignorance.