2/3 of our champ1 MMR matches have a GC in the opposing team. Not just 1 or 2; consistently. What happened?

So the 2 guys I usually play with are champ2 and dia3-champ1 level. I'm also champ1. NONE of us were ever in GC, not for a single match. We play 2v2s and 3v3s, depending on who's available.

This season we got absurd amount of GCs in our matches. Both 2v2 and 3v3, but 3v3 seemed even more infested with GC titles. Interestingly, whenever they actually say something about their rank, they say they are GCs in another game mode, or that they played a long time ago. But most of them still do stuff that we have never been able to, and the rest is just as bad as us, or even worse (which isn't too rare). But this many "GC in another mode" players, suddenly, out of thin air?

What happened suddenly?

Before this season, seeing a GC title in our games was definitely a rarity. We saw ~2-3 every season, and that was pretty much it. Whenever we ran into one before, they actually played like a GC and they hard carried their suspiciously clueless teammates. This season GC matches are more abundant than the ones without.

Is it because the player numbers are falling so hard that Psyonix resorted to widening the matchmaking search, allowing significantly better (or worse) players to match against us, just to keep the waiting times low? Now that I think of it, as many GCs we get against us, we definitely don't see just as many clueless opponents. If it's not the waiting time, then why did matchmaking change so drastically? Is it boosting? Because that didn't just happen overnight between the two seasons.

What do you think?

EDIT: People starting ranked at a lower rank than what they had in the previous season also can't be the reason, since we would also be somewhere in low diamond then; it's the middle of the season, so I doubt THIS many people whould start their freshly deranked season now.