Results do not surprise. Generally I think raises like that indicate a middle pair or AK, *not* a big pair like aces or kings. Jacks, tens, and nines are the most common. People are scared to play them post-flop so they mega-raise to get people to fold. There are exceptions but that's at least 80% likely to be true. I would just call and take a flop. Any ace or king is a golden check-raising opportunity.