Most of Azeri IFVs are BMP-1&2 and ERA is useless on them. ERA doesn't fully disperse the cumulative stream, so you still need certain amount of armor to stop it and BMP armor is not thick enough. Worse, detonation of ERA block could also cause spalling and crack the vehicle hull, as the Syrian rebels discovered the hard way, when they experimented with Kontakt-1
Not quite. Kontakt is tank-grade heavy ERA, so fitting it on lighter vehicles can only end in tears (or laughter, depending on perspective).
For BMP-3 vehicle, Kaktus in the name of the ERA system that is meant to protect against older RPG-class weapons (not modern tandem warheads though, you need heavy ERA + tank to, if you pardon the pun, tank that one), BMP-3 can be fitted with those, though I don't know if the Azeri saw fit to cough up for the setup.
It also seems the Azeri have more BMP-3s then -1s and -2s together.
They don't see through stone walls, they also require attentive and observant operator.
That much goes without saying, but having both would make sneaking in through foliage for example
much harder.
This new gear is not in production yet. Active defenses also have weak points, like the shrapnel vulnerable sensors and perhaps the distance at which this engagement took place could be too short for proper activation.
Arena is based off Drozd that goes back to Soviet Union days, but yes, at 20 meters the RPG gunner could well be under radar envelope.
BMP's don't need active defense in close range situations anyways since those explosive panels might harm all of its infantry it was carrying into battle who were undoubtedly helping defend the INFANTRY Fighting Vehicle from randos with RPG's sneaking to within twenty meters of it.
Actually that was the main concern and reason Drozd wasn't implemented, it had multi-tube launcher setup on the turret / above hull armour that fired explosive projectile, which in turn exploded in proximity of incoming enemy shot destroying / disrupting it's flight vector short of the tank.
It did the job but was
very hard on adjacent squishies, hence the system wasn't fully implemented. Modern ERA seem to have solved the problem.