Proof of Growth allows for people to be rewarded based on their community growth score. The 50% of the mining rewards gets randomly distributed in a form of a lottery every single block. Lets say someone has multiple accounts with large communities, they might get a high chance of winning the lottery, they never get 100% of the rewards.

Also invites are distributed randomly in a variety of ways as well.

So to answer your question, yes those with a big community may have a higher chance of rewards, but it will be extremely difficult -especially as the Merit network continues to grow the growth rewards get distributed across more wallet, limiting the return for any bad actors.

I hope that helps.