A large number of citizens protested his unilateral actions and his amassing or power. Those protests turned ugly and the security forces began killing the protestors.
But you know what, those protestors did not turn back. Watch this intense video of protesting citizens being gunned down...but others coming right up to take their place ad continue to advance. It is long, but worth watching. That was a group of dedicated citizens who knew the true value of liberty and their rights.
Would that our own people saw things so clearly.
When it was clear that the protestors were not going to stop and would reach the Government buildings including the Presidential buildings...the President fled. Then, as I said, the Parliament of Ukraine, strictly according to their constitution, impeached him and removed him from power.
If you are going to try and stand on the legality of his election, then you cannot have it both ways. he was also legally and constitutionally impeached.