Alienating existing customers is a terrible strategy

Existing customers of what? Akamai didn't buy a business (or if they did, they don't care that they did.) Akamai already has a business, one with (very profitable) customers. Rather, in buying Linode, Akamai bought another supply chain to use to feed their existing business-model with.

Think like: a sporting goods company buying a tire company, not to make tires, but because they want to sell their existing customers rubber balls to go with their knee pads and stickball sticks; and the tire company happens to have a good rubber-goods supply chain that can be repurposed to do that.

Akamai doesn't want to get into the VPS business. They want to repurpose Linode's systems to extend their "cloud-services integrated solution provider" solution portfolio. Remember "IBM SoftLayer"? Akamai wants to be IBM, and so they need a SoftLayer of their own.

It's been working for them for 25 years so far.

Akamai doesn't want you as a customer if you're not spending millions a year. It's not worth their time.

So, all they care about is the maximum cash flow,not the number of users or even clients.

It should take few brain cells to understand business is driven by return on investment and not "most burgers served"