One day, an incredibly smart and lazy matoran thought:
"Why walk on your own, if you can get a machine to do it for you?"
And after months of doing nothing because of his laziness, and just a bit of work, a the blueprints for a mecha were created, but seeing as how the matoran was impossibly lazy, he traded the blueprints to an engineer in return for the engineer not bothering him anymore. The engineer modified the blueprints slightly to make a battle mecha, and after months of not being lazy and working, he built the mecha.
Despite the mecha's unstable-looking body, it is actually rather stable.