this is definitely not the way to run any binary in a snap (and note that classic confinement does not make a difference here), you are breaking confinement and are also not using the correct environment this way … to run a snap application either use snap run <name of the app> or execute it via /snap/bin/<name of the app> (which should have been automatically added to your path when snapd was installed) anything else is broken and wrong.
also please note that there is no (permitted) way for a snap to create users or to run a daemon as a specific user beyond the “snap_daemon” user or root …
if the telegraf snap randomly modifies data in the systems password db this is wrong behaviour.