This isn’t what “being a big company that acts like a startup” looks like. This is what being a company that has a scatterbrained dictator for a CEO looks like.
Tesla isn’t building a robot because a scrappy team in the company discovered an opportunity for innovation. They’re doing it because the CEO suddenly demanded it between doses of amphetamines.
Tesla would look like a big company with a startup mentality if they were pumping out new automotive products that made some level of sense.
Hyundai and Kia more closely resemble what this would look like in a large company. All their new cars have unique bespoke designs and a laser focus on giving customers a compelling offering in every category.