@R4gn4r0k: Destroying the supply lines and waiting is still tyrion and varys choice, but dany wants to burn shit
Things went kind of how I would expected them to go: Since Cersei is ruler now and people are pretty uninformed, she can just lie about her attacker and make the people believe the usurper is just mad and is coming to kill everyone.
It would make a lousy first impression from Dany if she were to burn everyone, like the last mad targareayan. And I have to agree with the author of one article about the episode, that it feels a bit weird for Dany to rush everything like that. But hey, maybe she still has about 12 live service games to get to at home and she can't fall behind.