Municipalities in Turkey have the authority to collect taxes! They also receive funds from the central budget, if necessary. This is where the power of mayors comes from.
The total annual budget of the municipalities won by CHP in Istanbul alone is more than 30 billion dollars. The worst thing for the (AKP+MHP : = Cumhur Bloc) is that CHP won all of the mayoralties in the richest provinces!
It may seem that local elections in Turkey do not produce political impact because the central government does not change them, but the truth is not so. The money amounts controlled are very large, especially in the big cities. Of course, this much money will produce political results. This is the reason for this enthusiasm.
The reason for this dramatic difference is that the voters in power did not go to vote this time. I think the reason for this is that they are finally starting to run out of patience. Because the current government manages the economy poorly, but it also manages some institutions very poorly. Like the Turkiye Football Federation, for example. By bad luck for Cumhur Bloc, the scandals in these institutions broke out right before the election.