Yeah, when they realized people were really angry at the right wing option (Merino), Congress basically considered every other option over the weekend, and she was a contender. But at this point in the eyes of Congress it's more a "voted for impeachment/voted against impeachment" dispute than a left/right thing. That's not entirely unreasonable, because whoever gets in charge now will only get to be president for a few months, can't run again (one term limit), and won't be allowed to do anything very significant (have to imagine the cabinet will be caretaker civil servant types).
The protesters wanted someone who didn't vote for Vizcarra's impeachment, and the lib party which the new president represents is basically the only one that voted entirely against it (FA, the left party that 60/40 candidate represents, was split on impeachment).
if it wasnt for the shining path theyd be doing the whole populist socialist grassroots revolution thingy about now