It's fairly common to see fairly well-known people who at some point had identified themselves as being “Christian” very publicly announcing they are abandoning Christianity.
Another thing I've noticed is how very little of what a whole lot of people believe about God, who gets to spend eternity in heaven, and many of their beliefs on other spiritual matters is not true. Well how would I know it's not true? Well it's because their beliefs don't agree with what the Bible teaches.
People forming their foundation of spiritual beliefs on something other than what God gave us through the prophets, Jesus, and the apostles is not something new. In the new testament we can find this being called “falling for myths, wives' tales, or legends,” depending on your particular Bible translation.
[1 Timothy 4:7] But reject irreverent, silly myths. Instead, train yourself for godliness. BSB
If your Bible beliefs are mostly based on things like what your grandma told you it says, what the pastor you grew up listening to preached, or from listening to the lyrics of "Christian" songs, then it's possible you may not have as clear an understanding of the Bible as you think you have.
It's a wonderful thing when a person gives his or her life to Jesus. And that is true completely regardless of the kind of event that helped lead that person to Jesus. It is 100% perfectly okay for a recent convert to not know much about the Bible beyond what a person must do to be saved.
But it could not be a good thing to be on Jesus' team and remain clueless to what the Bible teaches. If you listen closely to some of the comments those leaving the church have to say, you might notice similarity in the statements they are making. Here's one example, “If a person can get to heaven without Jesus, why would I even bother with Christianity?” Well, they cannot because Jesus is the only way.
It does not seem to be that it is even possible for a person to leave a religion if they never even knew its particular set of beliefs or accepted them. These people aren't leaving Jesus behind they never knew him to begin with. It's only possible for Jesus' enemies to know Him and not want to be associated with him.
You might not know there are some problems with your foundation until you took a look at it. If you wanted to know the condition of the foundation supporting your home you could have it inspected.
Fortunately for us God does not leave us without effective solutions: With our permission, little by little, he will correct our thinking errors.
Examining scripture and comparing it to what you believe on spiritual matters is a cheap and effective means to confirm you have an accurate understanding of Jesus and what the Bible teaches.
Additional reading: [1 Timothy 6:3-5] 3If anyone teaches another doctrine and disagrees with the sound words of our Lord Jesus Christ and with godly teaching, 4he is conceited and understands nothing. Instead, he has an unhealthy interest in controversies and semantics, out of which come envy, strife, abusive talk, evil suspicions, 5and constant friction between men of depraved mind who are devoid of the truth. These men regard godliness as a means of gain. BSB