"During USSR" as you say, first wave of Russian immigration settled in West Berlin in 1920s running away from Russian revolution, so you probably did not mean that period of time. During occupation of Germany by Allies, both NATO and Warsaw Pact maintained significant military presence in Germany, but in 1990 Soviets have left (feel free to check it yourself in Karlshorst), Americans stayed. There was no migration of civilian Russians to Germany at that time, but DDR welcomed workers from other countries like Vietnam. Speaking of today, you can look at statistics on citizenship of Berlin residents: there you will find that, for example, more Indians than Russians are currently living in Berlin. And of course more Ukrainians.

Also this may influence the design of such data centers. A drone that a paramilitary group can build is not very sophisticated and won’t carry big payloads. Put an outer concrete shell or some better passive defense, and maybe that will be enough.

The same can be actually said about Zelensky, for whom any concessions to Russia mean political death too. If Ukraine loses territories forever, people will ask, why so many had to die for that. What was the plan. And blaming the West (which won‘t be 100% justified) will not help. And he may feel that now he is applying good pressure too, with those drone strikes and knocked out refineries.