MBS All Terrain Wheels and Cracked Hubs

I noticed today that both rear wheel hubs have a crack in them. While I’m waiting for new set to come in, I’m trying to determine where I might have went wrong. It could be all of these reasons but maybe someone has some pointers.

Could overtightning pulley do this? Would hitting some large crack in road at high speeds do this? Would overtightning the wheel lock nut once do this? Would using bearing spacers help this?

(To be clear, when I say hub, I’m referring to the part of the wheel the bearing sits in)

Bumb - this has happened to my evolve 97’s a lot as well.

Equally curious as to why and if it’s common.

I cracked another wheel since this first post. :frowning:

I think it’s to do with wheel pulleys, you it was the two rear ones where the pulleys are