But this isn't salvific. What they based their getting into the kingdom on is WHAT THEY DID. NOT WHAT THEY BELIEVED.
Wrong text. Stick with Matt 7:21-23. Matt 24:44 isn't in the context here.
They WEREN'T BELIEVING. They were WORKING. Why is that so hard to understand?
I suggest you read ALL of John then. You are wrong in your conclusion. Let's go back to John 13.
10 Jesus answered, “Those who have had a bath need only to wash their feet; their whole body is clean. And you are clean, though not every one of you.”
Do you understand what Jesus was telling Peter? Pete didn't want Jesus to wash his feet. Pete thought that was demeaning, even though Jesus was demonstrating serving others. So Pete got sideways with Jesus and told Him to basically give him another bath.
Jesus' answer to Pete in v.10 makes clear that all the disciples were already SAVED, except one, which was Judas.
The point of washing feet to "have a part" with Him relates to confession of sin in 1 John 1:9 and fellowship with the Lord.
Our sin offends God, and He won't hear our prayers when we are out of fellowship with Him. So, just as washing the feet of those in Jesus' day, who walked the same paths as domesticated animals resulted in very offensive animal feces on their feet, which needed cleansing, so our sins are even worse to God and we need cleansing.
So Jesus made clear that by ch 13 all the disciples except Judas were saved. And read John 17 where Jesus prays for His 11 disciples. Clearly He showed by His prayer that they were saved.