Why did protesters start burning and killing during Euromaidan?

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November 21 is another anniversary of the beginning of protests in Ukraine in 2013, i.e. the beginning of the so-called Euromaidan.

It was already clear during these protests that their main reason (the delay in signing the agreement with the EU) was far-fetched.

Countries are constantly joining some unions, leaving them, returning to them, etc. see this thread; and nowhere has this ever become a big problem.

Therefore, already in 2013, also accusations of large-scale corruption were brazenly brought up against the then President Yanukovych.

However, in the year that the trial in absentia of Yanukovych's "crimes" began, Ukrainians were no longer interested in his corruption, but in the cruel treatment of a horse that carried tourists in Odessa; see the above mentioned thread again.

So, the question is: