Since last year, transaction fees have been lower than they were in the last bull run. Right now, they’re still cheap, while in the past they sometimes went over $100. What caused this change?
As you have received from previous replies above, the cause was NFT ordinance, the got the mempool too congested then and we barely afford to see a bitcoin transaction with lower transaction fee getting confirmed, but aside that, the fee may also increase if the mempool is congested and once not, it reduces.
Will low fees last, or will they rise again if Bitcoin’s price jumps?
Fees don't rise along the market price of bitcoin, what determines the increase in the transaction fee is base on how flooded the mempool is or not, if it is more busy, then expect the transaction fee to increase because every transaction will be striving for it block to get confirmed by pumping their fee, while if the mempool is less congested, then we have lesser transaction and the least we can always have is 1sat/vbyte