CCleaner, but not Speccy and the others, routinely vanishes from my PC, running Windows 10, 64 bit. Several other programs are also being uninstalled without my say-so. My work-around is to download the free version of CCleaner and use it until it disappears again, but if anyone has a bright idea I'd love to hear it.
Could be the installed antivirus doing it.
Which version/build of Win 10 are you running?
And which antivirus (and version if it's not Windows Defender)?
Are you doing anything in particular when CCleaner/other apps get uninstalled?
What other apps are being uninstalled?
Windows itself will sometimes uninstall incompatible apps, and will remove older CCleaner versions, but it shouldn't have a problem with the latest CCleaner.
(Unless maybe if you are on an insider build).
Your anti-virus may also be uninstalling, or quarantining, things that it wrongly sees as threats.
(Or there is a slight possibility that you have a malware infection that your AV hasn't picked up).