They weren't giving him oxygen. They may not have been allowed to give epidrine (adrenaline) injections. They probably did not have a nebulizer.
Yes, we know they didn't have the patient on oxygen during the two minutes before he's placed in the ambulance; however, oxygenation isn't generally the primary concern in treating an acute exacerbation of asthma. Everything else you said is a wild guess and a disservice.
Constricted airways, respiratory exhaustion, and respiratory acidosis were more immediate concerns. He already wasn't breathing when they loaded him into the ambulance.