[Matrixbeast]

It's simple.
It took things more seriously after Go-On, add in Power Rangers' resurrection with massive advertising sparking interest in the original Sentai (Since every smart ass from the 90's couldn't shut up about "Hey, did you know Power Rangers is Japanese footage with new American scenes? Because I did."), and very easy to find subs.

So older Sentai fans itching for something serious got what they wanted and praised it, a variety of new fans hot off the heels of Saban and Nick's nonstop advertising got to see Sentai for the first time (And many value their first series as 'one of the best'), so they praised it for introducing them, and then just add in a dash of decent designs for rangers, mechs, and monsters, and yeah. You got yourself an overhyped blast.