An unfortunate and unintended consequence of counterattacking the invader. Very different from bombing a school due to bad intelligence in an unprovoked attack.
Ukraine has been attacking civilian infrastructure in Donetsk city since 2014. Even with the Soviet butterfly bombs you might remember from Afghanistan.
A more likely explanation is that butterfly mines were dropped by Russian armed forces; see Human Rights Watch:
Russian forces have used at least seven types of antipersonnel mines in at least four regions of Ukraine: Donetsk, Kharkiv, Kyiv, and Sumy.
There is no credible information that Ukrainian government forces have used antipersonnel mines in violation of the Mine Ban Treaty since 2014 and into 2022.
Of course this is all tradition to bring rebellious minorities back into Russkiy Mir, just look at how Grozny looked in 2000. That was Putin's first war, started when he was prime minister.
