cromulentenough:

some of the explanations from the wiki:

Although the existence of this effect remains uncertain, it is a
common belief amongst the knitting population, and several plausible
(and non-exclusive) mechanisms for the sweater curse have been suggested
within knitting periodicals and books:

• Unlucky timing. Knitting a sweater takes a long time, and the relationship dies of natural causes during its making.^[9]
• Rescue mission. The knitter senses subconsciously that the relationship is about to end, and knits a sweater as a dramatic gesture to save it.
• Catalyst for analyzing the relationship. Giving or receiving a significant gift such as a sweater may cause either the giver or receiver to evaluate the relationship.^[5] For example, the gift may seem too intimate, too domestic or too binding to the significant other. It can be seen as a signal
  that makes them realize that the relationship is not reciprocal,
  prompting them to end the relationship before it involves obligations.^[9][10]
• Aversion. The significant other may simply not want to wear anything hand-knit.^[3]
  A hand-knit sweater can also subject them to ridicule, either because
  the sweater looks bad (i.e., poorly made or unfashionable) or conveys
  overly domestic connotations.^[4][9][10]
• Misdirected attention. The knitter loves their sweater a little too much, and pesters the significant other about the sweater.^[9]
  Alternatively, the knitter loves to knit too much, and spends too much
  time with their knitting instead of with the significant other.
• Insufficient gratitude. The knitter sees the sweater as a
  significant thing, having chosen the pattern and color carefully, and
  having invested hours of labor; the recipient sees it as just another
  sweater, and the resulting lack of gratitude leads to tension in the
  relationship.
• New Interests. The knitter may have discovered a new aspect
  of their personality, previously unexplored, to be of greater interest
  than the receiver understands. Having joined a knitting community,
  spending all their time reading about and thinking about knitting,
  potentially being secretive about their new interest in hopes of
  surprising the recipient, which may manifest as reminiscent of
  adulterous behaviour, or loss of interest in the relationship, thus
  alienating the soon-to-be recipient.