My Theory - Religions Are Ways of Channeling Energy
Although each religion claim to be different from others in their beliefs, views, and doctrines, when you delve into the mystical qualities of each one, you find that they become more and more alike, with the ultimate goal of achieving "oneness" with all, and absolving one's ego and sense of separateness.
Even the most widely followed faith, Christianity, has mystical traditions in the Gnostics, for instance, which teach karma, reincarnation, oneness with all, etc. just like the Eastern mystical traditions.
Basically, I've come to realize that, despite the outer surface differences in beliefs and doctrines between the religions, what religions basically are in their essence are ways of CHANNELING ENERGY to grow, add to, and benefit oneself, getting in touch with a divine source.
Just as each individual is different, so each person has their own style of channeling spiritual energy that suits them best. And since each religion has a different style of channeling energy to its adherents, different religions work better for different people. There's no "one size fits all", for whether a religion or spiritual practice works for someone depends on how compatible their way of channeling energy is with it. And probably, the different religions, I believe, are all channeling spiritual/divine energy from the SAME source.
For instance, some people channel energy through the Christian faith very well, benefiting themselves, their lives, and their souls, so they stick with it and recommend it to others. Their feel fulfilled and their prayers get answered, so obviously it works for them. But others whose may get nothing out of it if their style of channeling spiritual energy is incompatible with the Christian faith. And this can be true even if they make a sincere honest effort to follow the Christian faith, for if it just doesn't resonate with their spiritual style and level, then it's not going to work, no matter how earnest they are about it. Instead, they may work better energy-wise with Buddhism, Islam, or other spiritual systems, deriving more spiritual benefit from them. Others may resonate better with more offshoot faiths such as Mormonism, Jehovah's Witnesses, or even cult groups.
Still, some don't need any religion at all. They may simply channel good energy to them just by going out into nature or the wilderness setting. Or they may simply meditate and channel all the energy and spirituality they need.
This is why, I think, why some people hear a religious message or gospel, and instantly feel that they've discovered "the truth", or sense that God or the Holy Spirit is speaking to them, while others hear the same message and consider it rubbish, nonsensical, and could never take it seriously. Different religious/spiritual paths and ways of channeling energy click with some and not others.
It's like with anything in life - drugs, alcohol, roller coasters, skiing, etc.; they bring pleasure and stimulation to some, while to others they do nothing or cause only discomfort.
Also, as one evolves or changes their level of consciousness throughout life and their spiritual path, sometimes one may lose their resonance with the religion/spiritual path they channeled their life force energy through best, which leads them to seek out a different spiritual or religious path. There are plenty of religious devotees who at some point in life, grow out of their faith or spiritual practice, feel stinted by it, and transfer to another one. For instance, some Christians may lose resonance with their faith, feel it doesn't make sense anymore, and doesn't work for them anymore, becoming Buddhists or adopting Eastern paths. And vice versa, for there are Buddhists who become Christians and find more fulfillment there and closeness to God, as well.
I was one of those, for instance, who resonated with Evangelical Christianity early in life. It made sense to me, gave me a powerful feeling of purpose, made me happy, and I even got a lot of prayers answered through it. But when I outgrew it, I no longer felt any energy from it, didn't resonate with it, it no longer made sense to me mentally, and my prayers were no longer even being answered. I tried my best to re-establish my spiritual energy with it, for I thought it was the truth, but it was futile, like trying to jump start a dead horse. I didn't realize it at the time, but my journey and path to truth lied elsewhere, and eventually led me to the New Age/Eastern paths. Therefore, I began subconsciously looking for excuses to invalidate Christian teachings, so that I could find truth in other teachings, considering all but committing to none. I discovered that I am an eclectic who loves intellectual freedom too much to commit and limit my mind inside the box of any religion or belief system, though I may make use of, see truth in, or derive benefit from them.