I had a similar disaster happen in my last office and the bitter/sweet feeling after...
From 2011-2015 I was a part of building something special, engineering embedded systems stuff... it was cutting edge, and fun! Amazing team of six, and we really pushed the boundaries of what was possible. I LOVED the job, and became an expert in it... I felt respected and valued for my contribution and vision. I was the youngest on the team (most were later in career), but had become the subject matter expert and was tasked to train the system at conferences. In late 2014 management rolled over, and due to politics in the office my mentor and PM got removed and pushed out the door... they replaced him with someone who wasn't technical, but had a lot of management experiences (apparently). It was really sad to see. The problem was that the mergers above him created a group who was threatened by successes and so they sought to remove what they felt threatened by. Really silly business model
Anyway, in late 2014 we got a new boss... this new PM didn't seem future focused, he was more aware of taking the easy path in things and redirected work in silly ways, then focused primarily on selling our selves, rather than actually engineering solutions. When I would meet with him privately, to discuss what had worked... the deeper level stuff seemed to bother him, he didn't actually want to know about it, so I lost the ability to communicate what I saw as innovative and improvements. He just wanted to hear positive news, and boasting about the latest numbers. He was more of a career business guy who ruled by tearing down others, and micro managing... problem was he wasn't technical. I fought with him for about six months, trying to tell him the disaster that was coming from his policies, and eventually I gave up and left, as well as 3 other members of the team around the same time.
What really bothered me most was that I was labeled as difficult and negative, when nothing had changed in how I was operating (I was just pointing out what I saw as coming; before it would help us avoid missteps; now it was just over the heads of people who preferred to hear rosy things, and seemed bothered by any mention that difficulty was coming)... I moved on to another group in 2015, luckily was also great work... really enjoy what I'm doing now, but it's not quite as good as that previous job. Just last month I found out that my predictions came true and the project fell short in all the areas that I was vocalizing at the time... the project was scrapped and the whole group removed. What's really sad is seeing something that I helped create and put so much into fall so sharply (and in avoidable ways)... the technology is no longer cutting edge or useful and it fell too far behind competitors
Lesson learned... it feels good to be right, but if you're right about a doom and gloom disaster coming... it serves no one any good to voice those concerns in a way that comes across as defiant.