I find it unsurprising that the outlets mentioned would take such a position, due to the lack of realistic alternatives. It's a classic case of settling for the lesser evil. If the question is meant to imply that these media outlets are naively optimistic about what the likes of Rohani will do, I don't think that is necessarily the case.
A 2013 analysis for CNN by Majid Rafizadeh was widely quoted in Western media when Rohani became president.
Although Rohani argues for constructive interactions with other
countries and although he supports applying a softer political tone –
as opposed to the combative, controversial and provocative language
that Mahmoud Ahmadinejad or other hardliners utilize – when dealing
with the international community and regional state actors in regards
to Syria, Rohani has not called for an overall sweeping shift in
Iran's foreign policy.
I think the phrase in bold is the fundamental answer to the original question. While it is accepted that Rohani is not changing Iran's foreign policy, it doesn't follow that the US would be better off with someone like Ahmadinejad in power.