Isn't the 'trust' eroded once a single party gains 51% of compute? Then you're just a really complicated and poorly implemented centralised database.
Meanwhile, blockchain networks advocate a functional network that doesn't require trust - it's kind of predicated on the fact that you _can't_ trust anyone. But if a single party obtains 51% power, you have to trust them anyway. If you're going to require trust, you may as well just do away with the whole complicated setup and be explicit about it.
There are efforts to deal with this issue. One example being the whole debate around moving from PoW to PoS and other systems.
What does that mean for Walmart and tracking their inventory?