"Only because they were routed (and the whole front in that region collapsed, basically) so quickly"

Not that quickly. [0]

"the usual scorched-earth tactic that is their calling card"

That's russophobic fiction.

"Blowing up that dam sure helped them get caught up towards that end"

Here is a Washington Post article [0] about Ukrainians attacking the dam with American missile to test if they can blow it up:

"Kovalchuk considered flooding the river. The Ukrainians, he said, even conducted a test strike with a HIMARS launcher on one of the floodgates at the Nova Kakhovka dam, making three holes in the metal to see if the Dnieper’s water could be raised enough to stymie Russian crossings but not flood nearby villages.

The test was a success, Kovalchuk said, but the step remained a last resort. He held off."

There were many more attacks on that dam by the Ukraine [1] but I won't bother to try to find non-Russian sources, the WP article is enough.

[0] https://www.washingtonpost.com/world/2022/12/29/ukraine-offe...

[1] https://pikabu.ru/story/skolko_raz_vsu_obstrelivali_kakhovsk...