> Tried to Google it but all I find is a bunch of American news website like CNN and website like https://www.voterstudygroup.org/publication/the-five-types-t...

> I'm trying to look beyond the propaganda, any idea if there has been scientific studies or anything remotely credible ?

Exactly, they "propaganded" so hard that they created a narrative that they are the definitive winners. So you bought into their propaganda and now you are surprised. The reality is that the democrats are not that good and the people voted.