Russia had to first survive long enough to get things turned around so they could take the offensive.
On the T-34s:
> To the Deputy People's Commissar of Medium Machinebuilding, comrade Goreglyad 8a Ryazanskaya St.
> In response to your letter #16/2291 on March 18th, 1941
> The GABTU considers it necessary to deliver the V-2-34 engine together with the main clutch for the following reasons:
> The warranty period of the main clutch is seldom higher than the lifespan of the engine: the engine's guaranteed lifespan is 150 hours, the tank travels 2000-2250 km in this time. The existing main clutch needs replacing after this time.
> The existing design of the main clutch on factory #183 T-34 tanks requires the following changes to be compatible with diesel engines received from factory #75:
[…]
* https://www.tankarchives.ca/2020/12/weakest-link.html
* https://twitter.com/Tank_Archives/status/1344342553911582722 (see thread on Kursk)
When the average lifespan in battle was ~14 hours, the stated 150 hours sounds pretty good.
I didn't know this, but I don't find it astonishing. This was when Russia was losing and the defense of Moscow was pretty desperate. It's likely a lot of those British tanks were lost during that battle (as noted, they weren't very good) and replaced with T-34s.
It's worth noting that most of the recorded losses of tanks by the Germans were in battles against T-34s.