OP must be very observant, there is always an increase in transaction fees when there is an increase in price and this happens because once the price of bitcoin begin to increase, the bitcoin network get congested due to the number of transactions that are being carried out on the network, miners will now have to work much more confirming transaction and that cause a delay in the confirmation of some transactions on the blockchain, since many of the transactions will have to pile up and wait to be included in a block.

Today BTC prices trying to break $5950 levels and at the same time blockchain.com showed me pending transactions up to 30k whereas my electrum wallet suggested very costly fees to be included to attract miners as quick as possible.

I guess when bitcoin markets into relatively peak levels, more people are buying/selling bitcoins or transacting bitcoins in more numbers which triggers higher tx fees. It is a correlations and could be identified easily for any bitcoiner .