When SF bought Heroku, it was something like, hey! We need to get on board with this cloud stuff. Our infrastructure using these pods of oracle + big iron no longer make good sense. So, as a multi billion dollar company what do they do. They don't pay for services, they don't build it from the ground up, they buy the hottest business on the market at the time.
For the first few years it was somewhat hands off. Let things gel and start installing SF leaders into the upper ranks on the Heroku org. Then the endless strategic plans to integrate and transition both advancing SF existing stacks and extending Heroku stacks with SF specialty hooks. Heroku Connect, etc.
The young elite engineers at Heroku had very little interest in build CRM product. So it wasn't necessarily full blown revolt, but rather total lack of enthusiasm and effort. Which led to some key firings in management, and more crony installation until the real heads of Heroku took the reigns and secretly put all future energies into SF integration to the extent that Heroku should ultimately become a product wing of SF much Einstein, Cloud..etc.
At this point, upper management told Heroku staff not to worry. Nothing is getting cancelled and every manner of 'remain calm' language. Narrowly curbing a full blow revolt. The key facilitators of which being coaxed into supplying company wide admissions that they were wrong, and everything is fine, and hurray, I love Heroku and I love SF. All of them were then discreetly fired weeks later, some of which continued the ruse, probably under duress, that everything is great and this is just a move based on growing a career and not dissatisfaction.
Over the next couple years, the typical corporate agenda played out of endless cost cutting, employee benefit slashing, and general freedom neutering. The talent by this point had drastically evaporated.
And here we are today. No talent to extend and create new services. No ability to keep pace with other cloud offerings. Continued denial about the true reality of what is going on with the business. With multi million dollar customers more or less in the dark about the fact they are running on what is tantamount to abandonware. Enter the first waves of service sun setting seasoned with a nice dose of kool aid.
You need to realize something else. Heroku was never unprofitable while SF owned them (possibly ever). It's just that the millions Heroku was generating was literally peanuts compared to the SF earnings. They needed to scratch an itch and thought they could do it by just buying the tool factor rather than the tool. The fact that they drove the tool company into the ground is of little consequence when you look at the numbers in play.
There are specific people who are directly culpable for the downward spiral of Heroku. Yes-men/women without a single stitch of the vision and drive that created Heroku and it's earlier success.
Heroku died in my arms years ago. It's all very sad.