Yea. I work as a software engineer at a company that sees huge swings in traffic on our product (by nature of the product). It's not uncommon for us to see 20x swings in traffic day-to-day. It's taken us a long time to be able to handle that and even then shit still goes wrong.
I'm much more inclined to believe the downtime is caused by scaling issues rather than some big conspiracy,
EDIT: Just to give some insight, one of the problems we run into is that usually only one issue is exposed during an outage. For example, lets say we have 10 functions (or services or whatever) in a row that all call each other. All the odd numbered ones have issues where they fail at scale. During the first downtime, function one will fail and start to throw errors, but this means the full traffic load isn't reaching the rest of the functions. By the time the problem is solved, traffic has usually died down, so function 1 is fixed, but 3,5,7,9 still have issues that haven't been exposed.
Additionally, at a quickly growing company like Coinbase, the code isn't going to stay the same for very long, so even once those functions are fixed, new issues are introduced.
It's easy to say they should be load testing at 10x their expected load to prevent these type of issues, but it's really hard to replicate production traffic. Users do weird and unexpected shit that can cause problems.