Why does it seem the devil is gaining ground, and Christians are losing ground? Perhaps because it is true a majority of the time.
Proportionally to when I was growing up, it's obvious that fewer people believe in God today and fewer people seek to serve Him even if they do believe. When I was growing up 50+ years ago, I don't recall anybody in my neighborhood or even adjacent streets that flat out denied the existence of God. On my street, the majority claimed to be religious and most families even attended a church services of some nature on a regular basis.
I don't recall this changing drastically as I approached being an adult, but I was able to recognize that fewer people that I knew were regular church goers. But as I got married and started my family, it was becoming evident that fewer people actually knew God and the proportion of those that were regular church goers to those that were hit and miss was changing drastically. Perhaps that was because my circle of acquaintances was growing, but it was true none the less.
Now, 30 years later, I know social media and having the world in the palm of our hands via our smart phones has opened our eyes to the rest of the world, but even at home, in my home town, fewer and fewer people seem to claim God and even fewer serve Him openly, and the picture is even bleaker when we consider that the vast majority of those that do claim God are 30+ years old.
Now, we could spend all day identifying why that is, but at least one thing is obvious, people aren't learning what they need to know about God. Yes, some chose to reject Him, yet others just haven't ever come to know Him because they haven't heard His message.
We still have people who need to hear the Gospel. Our lives are on daily display for these people, and we can show them Christ every day and hopefully persuade them to learn of Him, and ultimately obey Him. Initially, we may not need to utter a word, just show them love and share our lives. Then, allow the Lord to open the door to sharing the message.
We must plant the Word of God into the hearts of men and women so that it can grow, and in doing so, multiply the family of God. If we keep it to ourselves, it has no such opportunity. "Very truly, I tell you, unless a grain of wheat falls into the earth and dies, it remains just a single grain; but if it dies, it bears much fruit." (John 12:24)
Let us take advantage of the opportunities given us to share Christ with those around us.