Not sure I follow this. Salesforce bought Heroku over a decade ago and Heroku is still improving in its areas of expertise, with no signs of changing that.

If anything, Salesforce has been moving more of its core developer experiences over to the Heroku model rather than trying to make Heroku more Salesforce-y.

Heroku runs on AWS already, they're earning cost + markup as it is. If they purchased Heroku and did this, they'd be out several billion dollars plus lose their markup. Many of the Heroku addons also run on AWS, so customers may lock themselves into without knowing it. Additionally, customers are free to further lock themselves into the AWS ecosystem via "private space"/VPC peering.

And they have a competitor to Linode/DO in their Lightsail offering (though how successful it is in competition I'm not sure)