Don't feel bad. You fell for the ole' new beekeepers syndrome.
It goes like this.....
New beekeeper reads all about mites, gets scared the crap out of when attending the local new beekeepers course and hears about all the potential problems, hears all about how most beekeepers lose at least half their hives while attending the local club meetings, and so on.
But new beekeepers thinks that not dumping all those chemicals into the hive is the way to go. (and I agree) So he decides not to treat the first year. And whether they have 2, 4, or 10 hives, they all magically make it through winter.
This of course is where some really "bright" beekeeper automatically jump into queen breeding while plastering up a website and claiming to have "survivor bees" and has the magic answer for all our problems for us to buy. (Don't laugh...I've seen it happen)
The rest of the "lucky" beekeepers go into their second year with the confidence that they must be doing everything right, since their bees survived.
Then comes the second year "reality Kill", that has them backtracking and seeking answers.
So what happened? What most beekeepers in this boat did not realize, is that when they got those packages that first year, almost all package producers treat for mites just prior to shipping. So in reality, your bees were treated against mite loss that first year. Coupled with a natural brood break by the nature that packages are installed, you have overwhelming chances that the bees will make it the first year. This same type advantage is seen with nucs, coupled with brood breaks, the power of a first year queen, and other factors. Reality is that splits and first year nucs make it through the first winter in almost 100% of the cases.
So the first year is a given....any beekeeper doing NOTHING can have hives survive.
The second year is when mites begin to catch up and take their toll. It's this second year that is the most dangerous. It's this second year that most beekeepers actually get their first taste of a dead hive, and begin their education over again, into what it REALLY takes to be successfull at beekeeping.
I'm not saying all this applies to you. But this is the pattern of most beginner beekeepers. And it is repeated every year. The first year success is a freebie. The "new beekeepers" are really those in their second year.