> and of course RPG has no top-attack (unless you're firing from a building, which as we've seen is tricky to get it to arm in time)
These tanks were planning to assault Kyiv. The assumption was that cheaper RPGs (such as the AT4) would be used against these tanks. The AT4 isn't designed to be used vs main-battle-tanks (AT4 has penetration of 450mm), the frontal-armor is too thick (500mm to 700mm effective frontal armor, depending on the tank, depending on the angle the attack hits from... Largely due to geometry, not physical thickness). But the "cope-cage" might be strong enough to deflect an attack against the turret (especially if the AT4 is "top down", because it was fired from an urban building).
There's many, many, many weapons of war. There are many different types of "anti-armor" weapons.
The Russians also know that the turret has the critical weakpoint of the tank: the autoloader. If the autoloader is hit, the entire tank's munitions blow up simultaneously (aka: cooks off), and everyone inside the tank dies. Protecting the turret with a "cope cage" (even if ineffective vs Javelins) to try and mitigate damage from other RPGs (AT4, RPG7, Panzerfaust 3) just makes sense.
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Javelins are the most expensive man-portable anti-tank weapon. There's relatively few of them (yes, I know USA sent thousands of Javelins, but we also sent far more simpler anti-tank weapons as well). Javelins are $170,000 per shot, and the AT4 is $1500.
The other man-portable weapon discussed, NLAWs, are like $40,000, much cheaper than a Javelin but still an incredibly sophisticated and expensive weapon.
Media ignores the cheap stuff (AT4, RPG7) because they're not really interesting. But those are probably the workhorses and the more common weapon in the battlefield.