The answer has already been said in the 2nd post.
Video machines were really starting to up their quality - SF2 in 1991, followed by MK in 1992 - were the real game changers.
They are also significantly more reliable and need less maintenance. Therefore why would an operator bother putting a machine on site which needed a (paid) engineer to regularly attend and clean and fix it when he could put a video machine there which even if it took less coin drop would be more profitable?
There wasn't really a homebuyers market, at least not the size it is now, so manufacturers only had operators who put machines on site to sell to. When they turned their backs on pinball the demise was inevitable.
What then drove the nail in the coffin was the fact that arcades starting closing due to the home console market increasing - Play Station in 1994 being most significant release. It then meant that people could sit at home and play the same games they could play in an arcade. An arcade may have had a token pinball machine left, but with no new purchases, the fact that they were often poorly maintained (meaning a poor playing experience) they quickly dropped out of view altogether.
Once the arcades starting closing there wasn't even a token machine to be able to play. (The vast majority of remaining arcades then became dominated by redemption/ticket games because they were a high profit/low maintenance machine.)
