Doesn't take an ASE to see the only thing holding it on is a bent curtain rod and 2 nuts.
No matter how "strong and thick" the plate is, a chain is only as strong as it's weakest link.
Even a Wildebeest knows that.
All you had to do was cut a 4" x 6" steel or aluminum plate, drill 4 holes to match up with holes in the mounting plate, and bolt it on underneath the rack instead of that flimsy thing.
I guess it doesn't matter, it's only a little scooter anyway. And you sold that too, right?