There is no rule requiring that the root of the chord be the lowest note played…
In fact, you can create a wonderful variety of melodic and harmonic effects by using other chord tones as the lowest note.
This is called Inversion.
A C chord (C-E-G) played with its root C as the lowest note, called the Root Position, sounds quite stable…
The C chord can also be played with the note E in the bass. This is called the First Inversion.
You might recognize this from Eric Clapton’s “Layla”. In this case, the inversion is used to create harmonic instability and melodic interest in the bass line.
A C chord can also be played with G in the bass. This is called the Second Inversion.
This as a very common way to prepare to end a piece, where C/G functions as a double suspended V chord.