I'll bet he was getting a commission and bribed the govt employee to keep the commissions coming. I wonder if he got turned in by a competing church?
If you read the article, you will see that he had a property appraiser who appraised the the properties at below market value.
He would go to the government officials, who would give the properties to him as an intermediary for the church. He then sold them for a higher price on the open market, while giving the church only the lower, falsely appraised price. Presumably the bribes to the government officials were paid out of the profits he made.
Given this situation, it seems more likely that an official of the church that was being ripped off by Marek P reported him.
I'm sure they found out that a specific property which Marek told them had fetched X price was actually bought for Y.
I'm not sure how a "competing church" would enter into this.