I was running an arbitrage bot well before he claims to have started arbitrage and even back then, it was competitive enough that there weren't tons of money to

I was running an arbitrage bot well before he claims to have started arbitrage and even back then, it was competitive enough that there weren't tons of money to be made, especially considering all the risks and costs involved. In those days, a relatively common scam involved setting up an investment scheme that promised high returns thanks to "arbitrage trading" (but which was really just a ponzi scheme). I wouldn't be surprised if he was involved in something like that.