The offers with 12500 gems — Hunter’s Loot and King’s Treasure — are always offered to different players at different times based on some unknown set of criteria.
It’s been my observation that most people eventually seem to get them one way or another, but the timing can be radically different. I got them around 10 months into playing, both in a relatively short time, but other people seem to have gotten them in the first couple of months, and others take much longer, and sometimes they’re spread far apart.
Some players seem to have also never have gotten them, or at least don’t remember them. It’s possible that could be from starting playing too long before they existed, and having gotten other offers instead; or it could be based on purchasing/playing history.