that because they planned to activate pos at some point, and there is a difficulty boom now, which rise regardless of the hashrate, litecoin is dominant by asic, it's normal that the diff jump very high, and with the new l3 and l3+ it rise even faster, but no complain i don't like litecoin and i don't own any, i just ignore it altogether
Scrypt (Litecoin) only sees significant difficulty jumps the last few months when Bitmain starts shipping a new batch of the L3+
Innosilicon is still selling the A4 (and they just had to order chips for a new batch) but they're still WAY high on the pricing for the performance so I suspect their A4 sales are a LOT lower.
The reason difficulty was FLAT for ballpark a year was that NOBODY was making new Scrypt miners at all for a long time - Innosilicon had closed out it's last stock of A2 chips and had a long gestation period on the A4, and Bitmain apparently wasn't interested 'till Litecoin price started climbing noticeably due to the Segwit adoption threshold getting very close for a while.
Litecoin price is proving quite a bit more resiliant than most altcoins have been the last 2 weeks - it's even gained a little vs Bitcoin over that period. If it SAYS in the $40+ range, it might end up being the most profitable coin to mine pretty soon now, despite L3+ deployment in bulk batches.