Trademarks have to be Registered to be a trademark, thus they're on a database that is searchable before you even apply for a trademark. Thus ICANN could be in a very shaky legal position in the United States for even offering this
Are they supposed to investigate every entity that wants to create a domain name and see if there is an infringement? That could not be automated. If you make the registrar responsible for any infringements then they will have to charge thousands of dollars for each domain to pay for the due diligence, or get sued bankrupt.
Its the entity that orders and uses the domain that is responsible. Anyway, trademarks are not locks on words under all circumstances. Google any fairly common surname, You'll find dozens of trademarks using it, in different locations and trades. All can be quite valid.
People are thinking about the big names, it's the millions of small companies with trademarks that make this absurd.