While the first bikini was only worn in the 40's, the first evidence of crochet in history was in early nineteenth century Europe, where it was referred to as 'shepherd's knitting'.
Even so, when you gather both it will only take you back to the 70's. One of the reasons this type of bikini became popular again were creative outlets such as Etsy and Pinterest, where people look to create things with their own hands, whether for themselves or to sell. Creating not only more variety for the ones buying, but also the sense of costumisation, handmade, and uniqueness.
Despite that, the moment we are living in terms of style dresses three to four moods, one of them is very in sync with nature and culture, and it is the one you would see wearing a crochet bikini with some ethnic sandals or gypsy bracelets. Of course, this is not a rule and there are some exceptions. The best part of it though is that you could easily match the top with a maxi skirt for the evening or some denim shorts throughout the day, without looking like you are wearing a bikini.