Based on what I heard it was mainly cost vs benefit. It was mainly an expensive gimmick, as not only you had to buy more expensive equipment that had its limitations (expensive glasses that had to synchronise with the TV or very narrow fields of 3D), but also had to have channels with 3D (which might've cost extra) or more expensive media that was capable of delivering 3D.

While streaming could have been a contributing factor, due to it killing traditional TV channels and basically DVD sales, it seems that overall 3D cinema declined very fast as well. This is probably because how expensive it was for both cinemas and production companies, and production companies often resorted to cheaper alternatives rather than equipment that would actually film in 3D, leading to a much less satisfying effect. So as the 3D effects got shallower, the whole gimmick in theaters died, and probably the whole 3D fad.