There’s an element of confusion, it’s never black and white, you never truly know who are the sincere.
This is so that only Allah knows, and it is the inner reality that is given attention to, by those who seek Him.
If there was a clear way to see “these people are the righteous”, then some would wear that look to deceive.
If there were also clear worldly benefits to being sincere to Allah, then how do we even know we are truly sincere to Allah?
Trials and tribulations is the path to Allah, because only the sincere will remain on such a path. It requires a pure intention. Allah is the Most Pure. So we need to go through the fire of the purification process. In this life, or the next.