As it's usually the case with these events, it's easy to find motives if you discount the possibility of being caught. The US might do it for the reasons I mentioned. The German govt might do it to make the population more willing to follow orders. Some anti-capitalist group might do it because ... idk, trains are evil (they've been sabotaging mostly local trains in/around Berlin in the past decade or so, but they typically claim their actions, so we'll see). The DB might be behind it to get more money to upgrade & secure their infrastructure.
I'm pretty sure it wasn't me, but everyone else has a motive.
I'm sure that's true in general, and you'll never know whether you did someone else's bidding without realizing it, unless they tell you (but would you believe them?) or you uncover some huge conspiracy (but then who says that's not fake to make you do something else?). I vaguely remember an interview that Adam Curtis made with some British economist for one of his movies concerning stagflation and the general direction of the economy and wages at that time, and he said something like "when I can't sleep, I sometimes wonder whether what we did was exactly what someone wanted and they knew what would happen".
As for Die Linke, (the far-left wing of the) SPD and the Greens, I don't believe they're malicious. I believe they mean well, even though I probably disagree with them on most of their core issues.
You don't buy what? Why does there have to be "ideological friendship" for two groups of criminals to cooperate and root for each other? It has been obvious to anyone looking at actual actions made rather than words and political theater.
Its not like they even try to hide their location or anything.
If I was to put my tinfoil hat on I would say those current attacks concentrate on Germany because due to long standing influence of Russians on German politics German's political class is a de-facto ally of Russia (against the will of its own population). Those attack's purpose is to scare ordinary Germans into letting their politicians continue pretend they help while they continue doing all in their power to help Putin's regime(or its equivalent under a different name).