Step 2.6 Coinbase blocks your account citing "Suspicious activity"
Step 2.7 Sign up to three other exchanges, split the loot across them
Step 5 Argue with the bank about the source of funds
Step 6 Argue with tax agency that you'll fill out your taxes correctly
Taxing this is super simple, you just mark as "other" - akin to finding money on the ground.
Arguing with bank - which specific bank would cause problems here?
Step 2.6 Coinbase blocks your account citing "Suspicious activity"
Step 2.7 Sign up to three other exchanges, split the loot across them
Step 5 Argue with the bank about the source of funds
Step 6 Argue with tax agency that you'll fill out your taxes correctly