my acer griseum has died,after two years,why would it do that?

It could have been the two wet summers and a cold winter, as a combination they were lethal to lots of shrubs and plants. I lost an Eleagnus and a Hebe, and my contorted willow was very, very unhappy, although that is OK now after a lot of pruning.

You could take it back to the place that you bought it and kick up a fuss. If it was a reputable dealer they may replace it. You'll have to convince them that you planted it right and watered it etc. Is thr soil deep enough and did you dig it a large hole? Compost etc ..Bad luck. I try not to think about the number of plants that have died on me!!