What`s lacking about the Kerch Strait land bridge, between Crimea and Russia?

In this video, retired US Army General and former CIA Director David Petraeus tells CNN's Jake Tapper how the Ukrainian people have aided their army in killing multiple Russian generals. CNN has not been able to confirm the killings.

At 3 minutes 59 seconds, David Petraeus and Jake Tapper discussed military logistics around Crimea:

Petraeus: It's also that you have a land line of communication between essentially Russia and Crimea that doesn't require the bridge here.

Tapper: Let's go back to the corridor here. This is what they had previously, all they had was this teeny little bridge which you can't really get everything you need ...

Petraeus: That's right.

Tapper: ... if you're in the Russian military, across this bridge. It's just not big enough.

Petraeus: That's right, that's right.

Is Petraeus referring to Kerch Strait Bridge, a pair of Russian-constructed parallel bridges, spanning the Strait of Kerch between the Taman Peninsula in Russia and the Kerch Peninsula of Crimea?

Why isn't it big enough? What does Russia need to accomplish that can't be accomplished with this 'teeny' bridge?