The theory is essentially that the machines weren't properly secured, they cite some provision of AZ election law that I don't recall precisely which states that if the machines aren't air-gapped the election is invalid and must be rerun.
They think the routers are the proof that the rules were broken and thus will force a revote. When pressed they never can really articulate a specific theory of fraud, just that the rules were broken and they're upset when the rules were broken and their guy lost.