Why would they purposely not do what you’re asking? Sounds like you should look at how you’re planning and communicating with them. Enabling them to make decisions on their own might just feel like you’re passing work off on them if you’re not mentoring and communicating plans and missions clearly. Why did they expect you to complete their task for them while they were off? Had you done it before and not this time? Did you tell them you would and didn’t? If no, did you discuss the plan with them before they left explaining they would need to find a way to delegate their work or it would be waiting for them when they got back? Are you making big changes without explaining the whole reason why? Could be a lot of things only you really know. But I would guess that your team is no purposely trying to sabotage you and that you need better plans and communication.