In general a trademark is registered for a specific class (~industry). As long as the trademarks are for different classes and there is no risk of confusion, multiple companies/products can have the same name. For example Delta is the name of an airline, a computer company, a faucet company and a family of orbital rockets. There's little risk anybody would confuse these four, and they don't belong to the same class, so they can coexist just fine.

The US is quite generous in what you can trademark. In the EU for example you can't (as easily) trademark common words. But a quick search shows about 50 active EU trademarks on the word Tesla.