Why would you pull out copper and install plastic? Is there something in your local water supply that corrodes the copper?
It may have been a remodel on the cheap. (TLDR link)
PB was available with crimp-on fittings or with plastic compression fittings.
With the flexibility of PB and the cheap plastic compression fittings anyone could be a "plumber".
It was approved by National and local building codes for use in all applications where PVC was approved.
The failure for PB wasn't really the material, so much as the crimp-on fittings.
The were made of a hard plastic that didn't age well, was susceptible to certain chemicals in the water and also required a tool for each size (like early PEX), that was properly calibrated to the proper crimp size and crimping force.
As you can imagine many plumbers and wannabe plumbers just "knew" those expensive tools weren't "really" needed
PB itself was also susceptible to long term exposure to some of the residual chemicals of treated potable water.
"New" PB is still in use today, generally from the water main tap to the residential/commercial water meter and generally black in color, with metallic compression style fittings.
The "new" PB has been reformulated to eliminate chemical interaction with potable water and is a very viable alternative to copper in this application.
PB has not been available since 1996 when Shell stopped selling the resin required for its manufacture, due to the $1B lawsuit settlement it was force to pay.
PB is no longer allowed under National and local building codes.
FWIW, my own home was plumbed with PB when it was built back in the '80s. I have yet to have a single piping failure, but I did have 4 fitting failures.
Since the home has a crawl space, I remedied this by replacing
ALL the fittings with Shark-Bite fittings in the crawl space area.
90% of the in-wall piping has been replaced with PEX during various remodels and what's left will be replaced when the wife wants that room remodeled

Being on well water I expect this to be the end of it, from my experiences in the field.
If I have to replace the piping in the crawl space in the future (for some unknow reason), I'll simply use PEX and reuse the Shark-Bite fittings.