That is why i never use public wireless networks. I only use my own internet like 3g or at my home. I never use any other wifi connection just because of this problem.
This is the safest course of action, not just for crypto, but for your entire life (emails, social media, banking, etc). Public WiFis are unsecure and it is notoriously easy to compromise any data being sent through one. Using your phone's mobile data to set up a private wifi hotspot is safer if you absolutely must, but I only trade crypto on my home WiFi - no deal, no price, no dip is worth the risk of losing that much money.
Also, if this story is true, why did he spend €100,000 on bitcoin but didn't spend €100 on a hardware wallet?