Ukraine was never set up for “total war”; they sold much of their military hardware decades ago to raise foreign cash reserves. Apparently they attacked the Russian minority and culture within their borders expecting no reaction at all.
Ukraine demilitarised in the 1990s. Money was one reason. Ukraine was in severe pist-Soviet economic difficulties, just like Russia, but without the oil and gas to sell. Also Ukraine depended on the Budapest agreement to guarantee its security.
The events of 2014 (actually in 2013), began when the then-President of Ukraine, under Russian pressure, defied his parliament and went back on his promise to sign the EU Association agreement, a first step towards joining the EU. That was the real cause of the troubles, in that Russia (Putin) insisted that Ukraine remain an economic dependency of Russia. Everything else flowed from that.