It's either bad design or protection level equivalent to fat modern IFVs like CV90 and Puma.
According to
this it's armored up to 30mm APDS from the front and 14.5mm from sides, so there is some explanation for the weight, as this is way beyond what a Stingray, Sheridan, or Sprut-SD is armored against, translating to STANAG 6 front and STANAG 4 all around, yeah, that does sound like modern IFV, and similar weight follows.
Some sources mention ERA module option, which would also make it RPG resistant, what kind of RPG resistance do you think those Soviet light MBTs have without their ERA ?
This is, effectively, a medium tank, meant to be used in a similar role as a Stug, except with a turret. Why have no autoloader, 4 crew, and a big heavy turret to fit it, that's US doctrinal skew with tanks also spreading to totally-not-tanks, which has its pros and cons, but guess they have managed to make it fit whatever airmobility requirement this was designed for regardless.