He was ousted in an unconstitutional manner. Illegally.
"...This was the culmination of a series of simply bad decisions, one after the other, all made by Yanukovych himself...." False narrative. Ukraine and Yanukovich was a target of US/EU "economic hitman" practices. US/EU make an offer/demand to another country. If that other country does not go along with those demands, a whole number of things can happen. Revolutions, overthrows, assasinations, civil wars. All of these practices are detailed in a book called "Confessions of an Economic Hitman."
EU offered Ukraine a very one-sided trade deal, which didn't benefit the Ukrainians much. Ukrainian government declined US/EU backed a coup Democratically elected government was overthrown. A US/EU aligned interim government was installed.
