Todo estaba muy fácil.

But a previous sentence is ’ es más facil de lo que pensé’. Ser in one cas and estar in the other.

this confuses me as well. but I found the following in a forum which might give some indication when to use which:

I would say the difference is the same as in other cases of ser/estar.
If you say está fácil, you mean that in that particular case it is easy. If you say es fácil, you mean its always easy.
This work is easy. = If it is an easy job as a general rule you say “Este trabajo es fácil”. If it is easy at this particular moment you say “Este trabajo está fácil”.