CleanMyMac

Then you have been very, very, very lucky. That kind of software is a solution in search of a problem. It's like when you were a kid and asking your mother to clean your room. I'm guessing you either don't use your computer very intensively or you are just used to it running slowly.

https://macpaw.com/support/cleanmymac-3/knowledgebase/how-to-uninstall-cleanmymac-3

Antivirus tools don't really do much on a Mac except work constantly and taking away resources that other programs need. A bit of smarts in not doing stupid things like installing software from web sites scaring you into thinking you have a virus (Windows does, not Macs) is all it takes. If you should get malware on your computer (I have never seen any -- you have to try hard to get some) there are better tools you run once and then let them sit unopen.

By all means if you are happy with those things then fine; it's not my computer. I'll look forward to seeing you sometime in the future when we help you reinstall your operating system (something I haven't done on a Mac in a quarter of a century). :-)

It's also known around here as Cream My Mac. Cleaning apps are not only unnecessary, they are all known to remove things they shouldn't. Like system files. Or items that are important to your third party apps, but the "cleaner" thinks is something to remove, breaking one or more apps in the process.

Why not?

There are several topics each day where somebody says their computer started running slowly a few days earlier. We get them to run a tool checking software they have installed and tell them to remove Clean My Mac. They do that and then post back saying the computer now runs normally again.

No, no & no.

Is snake oil necessary?

Mac can take care of itself.

The only thing you need to do is to keep it updated and don't download stuff other than directly from the app developer website.

Don't touch it, or anything like with a 39 and a half foot pole.

Clean My Mac is best removed using the manufacturer's own methods outlined in the link I provided. It tends to have bits and pieces scattered about and while it can be ddone manually it definitely falls in the class of having to search many, normally rarely visited locations on your computer. I don't know about removing Bitdefender, maybe their web site has uninstall tools.