Clearcoat Bed Liner Preventing Cedar In Contact With Dirt From Rotting?

Preventing cedar in contact with dirt from rotting? - clearcoat bed liner

I built 2 increases cedar planters worked last summer.
I have 3 layers of latex paint sealant in them.
They sat in direct contact with the surface soil in winter and were covered with snow.

This spring, let's say 8 months later, I decided to dismount in order to build a huge bed in place.
Rotted 3 of 4 tables that were in contact with the ground!

I thought that the cedar should be more resistant to decay.
Is there something else before a new bed, lest it destroy in a few years need to be addressed?

Better not to invest in a large gravel bed, and not, but this is a good solution?