The Russians/ Soviets have a long history of tank guns with calibres larger than those in the West, in fact they planned (built 1 prototype vehicle - Ob'iekt 120/ SU-152) a 152 mm weapon some time back (1965 for the built vehicle).
1 metre penetration isn't "excessive" (i.e. not unexpected) although it is considerably better than the one mentioned (that managed 290 mm at 2000 m), for example the German DM-53 round is said to penetrate 760 mm (at 2 km) and the US M829A3 is about the same (765 mm at 2 km). Oh, and the Russians claim that the 125 mm 2A82-1M currently fitted to T-14 is already
capable of penetrating 1 metre of armour at 2 km. So why would they want to shift to a larger calibre thereby reducing ammunition on board?
As for marnix's question "but does armour that thick really exist ?" the Leopard 2 (latest version) is said to have at least 1 metre of armour on the turret front.
It would be interesting to see if they actually bother fitting a gun of that calibre (the 1960s version had a barrel over 9 metres long!), although it has been mooted for quite a while by Western sources that Russia would increase the calibre from their current 125 mm. Then again, 135 mm has been bandied about as likely.
In contrast the West looked at 140 mm weapons for quite a while (and fitted them experimentally to various platforms - Leo2, M1 Abrams...) before deciding that ammunition improvement gave all the power needed to counter Russian tanks. That may change with Armata coming in (gradual) service as I noted on Quora a while back:
I do, however, find it highly intriguing that the Russians have gone for something that appears to be at least the size of their current MBTs.
Given a smaller turret (and therefore a much-reduced armoured volume) I'd expect it to weigh significantly less than the extant types .
If they'd accepted THAT weight reduction then they could have opted for a smaller power pack (while maintaining a similar power/ weight ratio) which would, in turn, have reduced the armoured volume leading to further reductions in size.
They could have ended up with a much smaller and lighter vehicle while keeping armour thickness to current standards - that they haven't done so leads me to think that A) it's possibly significantly better-protected than the "usual" T80/ T-90 series vehicles or B) there's some other surprise to be revealed.
The secondary armament - supposedly a 30 mm 2A42 (Wiki ) would add some weight back but it's also claimed that it uses "new type of lightweight armor" (Wiki again) - so why does it weigh 10 tonnes MORE than T-90? 
1 Modern MBTs have up to one-third of their weight in the turret, although Russian designs, with an autoloader and generally smaller turrets anyway don't reach this value.
2 Armata Universal Combat Platform
3 This adds to my point A - maybe they've gone for massive protection (after all, the US is/ was recently looking at their next-gen MICV having a weight of 65 tonnes to incorporate protection levels indicated as necessary by action in Afghanistan
1 Apparently this from the current L/55 barrel of the Rheinmetall 120 mm gun.
2 And that's composite, not RHA (Rolled Homogeneous Armour) which is the "standard" used when penetration values are given: i.e. Leo 2 has, effectively, considerably
more than 1 metre of thickness.