The stuff was getting out either way. Controlling the release was rather better than an unpredictable explosion, even if a poor option itself.
I disagree.
There were many many far better options.
Certainly not all the tank cars were at risk
If they were, you vent them and fly in some fiberglass swimming pools or anything but what they did.
If it is really that volitile it should not be traveling in a statistically unsafe manner.