People seen a decent price growth. Someone tried to sell his BTC for fiat and fix profits, someone tried to sell his alts for BTC because it is more stable and got more growth then some alts. With a fast growth people had a million reasons to use their Bitcoins and now, when the proce is stable for already some days, everything returned to previous numbers.

no it was not coffee purchase and it was not spam attack. it was price rise.

each time bitcoin price rises a large number of people (the traders) start moving funds around:
- from their wallets to exchanges to sell and take the profit
- buying on exchanges out of FOMO or as they see the rise signal and moving it out of risky exchanges back to their wallets
- dumping altcoins and moving the bitcoins they receive to bitcoin exchanges or to their wallets to sell or hold.
and all that increases the number of onchain transactions drastically.

I don't know if you have heard this news More Than 30% of BTC Traffic Stems from the Veriblock Project . So prior to the sudden spike of the price, mempool have been somewhat clog already. And when the price goes to more than $5k, lots of online trades pushing the mempool + the supposed 30% from VBK project to a bottleneck. But it seems the hype have run out of steam for now and settled the price around $5k and mempool went to 'normal' again.

Traders are quite busy monitoring BTC's price. They're all playing inside the exchanges like a casino and will not quit and withdraw out until the volatility calms down again. Nothing unusual I guess.

My thought is that it has to do with the fact that many traders are boycotting Bitcoin for other means of payment coins. A few days ago, a friend complained of a blockchain transaction that took over 24hrs to confirm. So, what trader or businessman would want such a delay for something they could easily do within a few minutes with Litecoin or BCH?

Boycotting BTC? Seriously? That is your theory? You have got to be kidding. Its pretty obvious that the spike in the price of BTC value or Veriblock are legit reasons behind this problem.

Also, the LN is being improved to tackle the very problem that you mentioned.

The short-term FOMO and hype has since died out after the price has stopped increasing. It's normal for people to move funds around from wallets to exchanges and vice-versa one huge price movements are observed and are recorded. Most traders surely don't want to miss a thing when this happens, and so in order to be in the action when it happens, they are transferring their funds together with a lot of people trying to cash out within the same time. In the coming days, expect the mempool to be cleared of such hindrances and backlogs as the trading action, once again, settles @ $5000 and becomes stale.