There are a fair number of common factors. One that gets insufficient attention is that both leaders were aging and rapidly losing their grip, and that in both cases the plans for succession were shaky and involved family members widely seen as inadequate. We tend to focus on the reasons for growing discontent within a populace, without realizing that these events are often driven less by discontent rising to a tipping point than by the leader's control declining to a tipping point. Peaceful rebellions succeed so often because they don't usually happen until it's clear that the leader no longer has control. Of course in the Philippines the leader's incapacity was evident far before the tipping point was reached, allowing more preparation.
At the risk of diverting the thread, though... the US role in resolving the events in Manila in '86 is substantially overstated. There was a great deal of dithering, and the US action was not decisive, nor was it at the peak of protest: by the time the US acted the matter had already been resolved on the streets. This is not entirely a criticism of the US - it's not always a bad idea to see who's going to win before committing to a side - but it would be inaccurate to refer to the US action as "decisive". It did avoid a very unpleasant end for both the rebellion and the Marcos family, but it did not affect the outcome one way or the other.
Having been right in the middle of that particular affair from beginning to end, I'm often struck by the extent to which the official records (there are a number of varying ones about, mainly arranged to serve the interests of their sponsors) get it wrong, despite the heavy media coverage. Not that I ever fully trusted the official record of anything, but it did place the deficiencies in stark relief.
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