To gain territory you need to attrite and degrade the enemy response. This does not require massive number nor a "x5". A basic example: you blow up the Kerch bridge, all supplies to Crimea have to make a dangerous route of hundreds of kilometres more. You have killed 0 people, but the frontline is not getting ammo and they are forced to retreat.
...
I don't want to piss in your Cheerios, but when the 'Ukrainians' went full al-Qaeda and did the suicide truck bombing back in 2022 it stopped rail traffic for a whole two days or something IIRC. Vehicle traffic was inconvenienced by having to share a span while the collapsed one was re-built.
Supposedly there was a later British attack with Storm Shadow missiles, but info on that is sparse at best. May even be just another 'Institute for the Study War' (familiar neo-con Jew clans working their American gimps) fantasy.
In any event if/when necessary there are ferry boats that can work the straights as they have for about 100 years. But even then, why bother? The alternate route through now-Russian Federation properties adjacent to Crimea are and all the way over and up into the Motherland are not much more dangerous than any highway in the West.