Wifi absolutely prevents sleep. It does so through a mechanism called "surfing the Internet on your phone in bed." Ditching the wifi and switching to wired Ethernet won't save you from this phenomenon either! The problem is a sleep endangering device that's designed to shoot particles (which also behave like waves) directly into your head! It captures the wifi signal which the device uses to reconfigures its photon emitter, which will disrupt your sleep.

The only solution is to leave your phone on the other side of the room or if you can help it, another room entirely.

But seriously, sleep hygiene is an important aspect of basic hygiene that should be more broadly taught, but isn't.