Did they fake hearing from God and knowingly lead Israel astray? Truly hear from God, but like v15-20 they were hypocrites regarding their message?
Every individual case is different I suspect. It is possible to not fake hearing from what one believes is God and unintentionally lead astray and is - in my opinion - representative of the vast majority of those involved in false teaching and prophecies to this day.
Case in point: a pastor of a charismatic Assemblies of God church I attended years and years ago.
They ministered in the gifts of tongues, prophecies, interpretations of tongues etc. - both ordained leaders and lay members. I was one so ordained as one of the leaders. I can only speak for myself in my level of sincerity.
Enter a tragic case of a young student athlete in the church stricken with cancer. Unlike all other requests for healing and prayer and faith, this one was so young and so "unfair" in the eyes of our church that the prophecies and charismatic gifts took on a different tone. One of urgency and pleading even harder than they had for the elderly facing the same prognosis. This was my first inkling into the flesh being operant - at least in some part.
Feeling the extra burden of this case, my Senior Pastor felt called to Toronto to get an "extra measure of anointing". It again struck me that historically this had never before been the case.
I did not go to Toronto. But several members joined him. They came back "on fire" testifying of new utterances "in the Spirit" and visions of flames dancing before them and "confirmed" when they asked each other if they too saw the flames and each affirmed they too saw them.
Shortly after this, when the young man came forward on a Sunday morning for prayer, it happened. One of our lay "prophets" prophesied complete healing and specifically prophesied that the young man would play ball for the team that drafted him (an MLB team to be precise).
He never played ball. And passed a few months later.
This pastor I am focusing this tale on did not accept this at first. He believed. With all his heart, he believed. So much so that he went down to the funeral home and asked permission to pray over the body before embalming. He was praying for a literal resurrection event.
It did not occur.
I lost my faith completely by this point - only to find God's grace in saving me some years later and securing me to a tradition of Reformed theolgy. All praise to Him for that.
The pastor did not last long at the church. Everything was fine as far as it went, and everyone was still worshipping but the "fire" was missing.
He took a new church across country shortly after, and I heard of new gifts and visions every once in a while before he went to a new church in a new state a few years there.
I talked with him many many times and he never lost faith nor passion nor energy in his false teaching and false prophecies. He genuinely believed he was working in the Spirit of God ("G-aw-oh-d" with multiple syllables when he was excited enough at the pulpit).
From the outside, I concluded he was genuine and intense - intense to the point where he would take a church and in a coupe years work them up to a point of growth in numbers and he would seek a sign of significant stature. A sign that writers would write about. A sign that would make his address one to mention alongside Toronto or Brownsville, FL or Azusa Street.
When that would inevitably fail, this pastor would after a couple of months of cooling be "called" to a new church where the cycle would be rinsed and repeated.
I knew him well. As well as anyone can know anyone I suppose. I do not believe for one minute, he was disingenuous or even self-aware enough to realize his patterns until closer to his elder years. Even though I can only surmise from how he talked when reflecting back.
My only personal takeaway is that I was no different and only by the grace of God did my road take a different path than his.
I don't know if that helps you in any way with your question, but take it for what it is worth and in the spirit I offer it.
Read your Bibles, go to Biblical churches, and remember not all false teachers and prophets are big names on TV and have luxurious lifestyles.
God bless all