My pet theory is that RM Optimus Prime was designed as a companion piece to MP-01 for kids, with no idea how they were actually going to release the thing, and Robotmasters was subsequently cobbled into existence. There was no broader plan for what the line was supposed to be. They just needed a vehicle to get their mini MP-01 into stores, and they threw together an excuse line with an excuse plot.
They did hit on the idea of making other mini (and toonier) versions of larger toys, and that was fun, but they weren't given time to refine any of those designs because they weren't the reason the line existed in the first place.
They did hit on the idea of making other mini (and toonier) versions of larger toys, and that was fun, but they weren't given time to refine any of those designs because they weren't the reason the line existed in the first place.