Germany did not ignore Russian military invasions, which can be easily demonstrated by specific actions that German government took at that time. Notably those actions were not much different from what USA or other European countries except a few with anti-Russian paranoia did.
Besides, there were two, not three invasions. Chechnya is not a country.
There was a Chechen Republic of Ichkeria that existed until getting slaughtered, occupied, and retrospectively written out of the books by Russia.
Yeltsin (and later Putin) was a baddie that West hoped to trade with, so they were willing to push aside the issue of Chechnya calling it an internal conflict.
But in reality the level of Russian war crimes was unparalleled, sometimes even worse than what's happening in Ukraine.
Internationally no high-ranking Russian officials or military officers were ever prosecuted or actually condemned for these war crimes.
Chechnya as independent country did not exist in 1990s. There was no legal mechanism for it to leave Russia, no democratic process to leave, no recognition by other countries etc. Separatists committed numerous crimes against civil population in Chechnya and outside it and eventually switched to terrorist methods, attacking schools, hospitals and cultural events (e.g. Budennovsk, Beslan, Nord-Ost). Basically, they were Russian version of Hamas or other radical organizations in Middle East. Not the type you would ever negotiate any independence with.
