Actually there is several period detected in the brightness, one being ~420 days (give or take 10 days or so), another is ~2100 days. Several of those having a (nearly) simultaneous minimum might very well explain the stronger than normal dimming we just have seen. The other thing that got some attention is that Betelgeuse did not start to rebrighten January twenty-something -- like expected -- but reached a minimum slightly later, on February 10th or so. The correct conclusion of course is not "it is blowing up" but "we got the period length slightly wrong", closer to 425 days or maybe the period length is not exactly constant.