What other Trask would have created it? The disposition of Bolivar Trask’s Master Mold is known. It’s toast. Larry Trask’s Master Mold for the Mark II Sentinels was never revealed. That leaves the only possible Master Mold Casandra could have used was the mutant Larry Trask’s Master Mold. We know it was a Trask Master Mold because it needed a Trask to activate it.
Also, saying humans created the Sentinels isn’t quite correct. Yes, Bolivar Trask was a human and he created the Sentinels. But it has been revealed his mutant daughter Tanya helped program the Master Mold secretly. So, mutants were in fact directly involved in creating the Sentinels. Robert Shaw was not the first mutant ro build Sentinels.
Yes, Larry Trask was self hating and apparently Cassandra as well. But they still built Sentinels and Casandra committed the Genoshan genocide. It’s not the case that humans caused the Genoshan genocide.