Before all these events in 1989 the USSR elite had given clear signals not only that they will not interfere, but in fact they actively encouraged satellites' independent policy. I remember some of the reported friction between Gorbatchev on the one hand, and the most rigid leaders on the other, specifically with Honeker and Zhivkov. All the work Gorbatchev and his circle had done made the subsequent changes in 1989 possible.

Btw, as a matter of fact Chaushescu was not exactly "overthrown", but after a mock court murdered by his own security services live on TV; not as savage as the execution of Ghadaffi, but still pretty shocking back then to happen in an European country.