Being a small, not particularly densely populated state helps, but our case rate per 100,000 people is still the lowest in the country, at 281. For comparison, Florida is the 3rd worst in this matter at 3,290.
And Vermont actually does see quite a bit of tourism. Hiking, mountain biking and camping in the summer, foliage viewing in the autumn, and skiing in the winter (I've talked to a surprising number of Floridians at Stowe and Bretton Woods in New Hampshire). Only in the transition between autumn and winter and spring mud season is the state usually rather devoid of tourists. Hotels have just recently reopened, for an idea how seriously our governor took this pandemic (he's Republican, BTW).
There are some unique structural reasons why Vermont has kept the case rate so low, but a lot of the success comes down to just doing the standard things correctly.