OP sounds like "don't use Bech32 when bitcoin is congested"
That's the opposite of the truth. Blocks can be made bigger if it contains segwit transactions, and bech32 is the most space-efficient segwit address type. Bigger blocks will relieve the congestion.
there was a lot of shit going on by that time, it was not jut BCash team spamming bitcoin network. there was the price spike that always increases the number of transactions, it was other altcoins trying to get pumped so they spammed bitcoin (like Dash), it was miners that were speculated to be involved in the spam attack to earn more money, it was a bunch of altcoins which were using bitcoin network to mine their coin by making pointless transactions on bitcoin chain, and a lot more...