Let's take a look at the context of Malachi 3:10 with the rest of the Bible. The more I think of that there'st not enough room to receive it that it means you're to share your blessing with others. But it doesn't mean that God exempts the faithful from trials and tribulations in exchange for faithfulness. On the contrary, the more faithful you are to God the more the world will hate you (Matthew 5:11-12, John 15:18-19, James 4:4). The more the Christian will be faithful in giving money for the work of the LORD the more the world will say that the person is a lunatic for doing so. To be faithful in one's service to God is a huge loathsome sight to the world that loves sin.
How do crooked pastors work use the doctrine of tithes and offerings for their dirty work? It's not just merely emphasizing on giving tithes, offerings and first fruits. One may observe how these crooked pastors end up living in mansions because their pulpit willfully gives them that cash. Much cash is raked in for a pastor who appeals to their lusts (2 Timothy 4:3), who preaches only good things (Isaiah 33:10) and remember even today, people still love the ministers and false prophets who bear rule by their means (Jeremiah 5:31). A pastor after God's own heart may get tithes and offerings but it won't be enough to live in a mansion because he doesn't preach the prosperity gospel. But a prosperity gospel preacher can get all that money from the tithes and offerings because he preaches the prosperity gospel.
Here's what happens: the tithes and offerings aren't used for the glory of God and to do His work to reach others out for the Lord Jesus Christ. Remember the tithes and offerings in the Old Testament were meant to support the work of the LORD. It's supposed to sustain missions and charity work. But what these pastors do is to use the tithes and offerings for their personal use. What's worse is that while they misquote Malachi 3:10 yet they have robbed God. They robbed God in the tithes and offerings when they use the money for their personal gain. It's a huge misuse of tithes and offerings that not only have they conned people into paying up for promises God didn't make for those who lovingly give their tithes but also, they have used that money for their personal gain.
What's worse is that many of these prosperity gospel preachers actually work with the Vatican yet some Roman Catholics tend to deny it. Joel Osteen has been working with the Vatican for several years now and the fruits of his action are definitely not any evidence of being born again. He's not a born again pastor but a burn again pastor because his works show he's not saved to start with (1 John 2:19). He's definitely going to burn again and again in the Lake of Fire when he dies in his sins. Many prosperity gospel preachers will be burn again preachers that first they die and go to Hell and on the Great White Throne Judgment, their evil works will be exposed and that they'll be sent to burn again in the Lake of Fire.