Eight strange flights booked with only my email

Earlier today I got 3 separate emails from a foreign airline I hadn’t used in years. They were 3 different booking confirmations, 8 flights in total. At first I freaked out thinking I had been hacked, but then I realized I didn’t recognize the payment method (a Master Card with last 4 digits that didn’t belong to me) nor the phone number used in the purchase—they literally just used my email for checking out. They even used their “own” reward points, so they clearly logged in with a different account from mine. I have all of the 8 passengers' full names and DOB, and the strangest thing is that all the flights were the same round trip for today, then the return trip just a few hours later but from a completely different city far away from the first destination. I called the airline and they were completely stumped as to why anyone would do this. Either way, they just cancelled the reservations. I also know someone didn't just open a new credit card under my name because my credit is frozen and I already checked my credit report. I’m just wondering, what is the scam here? Even if it was done with a stolen credit card, the scheduling of the flights would make them pretty much useless, not to mention extremely trackable since they used real names and birth dates.