Why does this website kill my battery so fast?

Because you don't have a desktop PC

Well, the notifications seem to update in real time. This means it must be constantly sending out requests at some set interval. I've noticed with my phone that wifi and data usage tend to burn through my battery life faster than viewing offline video.
Edit: Also, as Darksky mentioned, there are ads which refresh themselves too.

If you're running it through orbot or similar, it will. Even if you're not, though, your data is in terms of megabytes.

Turn notifications off or it is constantly is trawling for them

💫 data collection

The ads

use laptop or PC. Lol