If multistatic radar was deployed and operational, then how come the
US, NATO, France, UK, Japan, and Saudi Arabia invest so much
money in maintaining a "monostat

Every monostatic radar could be part of a multi static system,alongside TV
,radio and phone emitters.You dont even need your own or friendly radars,even
hostile emitters too will do the job.
What you need is only atmosphere filled with EM waves.
But they have shortcomings too,they might be more vulnerable to some ECM
methods,their low altitude performance might be poorer than convantionel
radars.(Even though US counter LO system has been optimized to detect next
generation stealthy cruise misilles and UCAVs using terrain masking)

Why they still invest in convantionel radars
(and stealth platforms)?
Well,Mitchell has showed whole world in 1921 that the era of Battleships was
over,but the Admirals all over world continued to built bigger,better and more
expensive battleships till they learn the truth hard way during WWII.

That information alone should tell you how significant multistatic radar
has been integrated into defense systems. I can appreciate one transmitter,
multiple receivers, but using it to shoot down aircraft and track them
through the national airspace has

One emitter multiple receiver type multistatic,even tough theoretically
possible,would be the worst solution.


I think your either dreaming, or incorrectly extrapolating what you
read in Aviation Week, or Time magazine.

None of them published passive radar images of f117 as far as I know.