There were periods when blocks were full throughout the whole year, not just at the peak of the bubble.
True. and the fees got mighty high at those times too, for example there was a period from Apr '17 to May '17 when the blocks were nearly all full. During this period the mempool size peaked at about 150Mb, but in the December spike it doubled to 300Mb.
The charts only show that the fees follow the price, which is logical because higher price -> more people sending coins to exchanges to sell.
Nope. There's a non linear relationship between $ fee and BTC price. The fee in satoshis increased too.
Why would people dump Bitcoin just because the fees are high? Most of the complaining came from bounty hunters and microinvestors who usually deal with double digit amounts. These people don't have any big influence on the market. People who held multiple coins didn't mind paying a $30 fee to cash out their 10000% profits.
I think a lot of investors around this time did not understand the technical limitations, and this was the first bubble where the 1Mb limit actually came into play. And the $30 fee would not have remained $30. It would have gone up had the bubble kept going. Who knows how high?
I think there was a large contingent of smart money who saw the crash coming and sold once the fees started going mental, but it's hard to argue that there was a strong correlation between hitting the 1Mb limit being hit... I mean just look
here, take a look at "Pending transaction fee in BTC". It's clear to see that the fees (in BTC, not $), went mental just after Dec 16th.
It's hard to argue that the fees didn't play a role, and the fees are dependant on the block size.