Bezos delegated, but he also followed up aggressively, and the whole company reporting structure was designed to enable that.
When I worked there, Bezos held a weekly S-team meeting where the execs all came fully briefed to answer any questions about ongoing issues in their departments. That flowed on down the chain: Andy Jassy had an AWS-wide meeting the day before to gather the relevant data from each of his teams, and that meant that every major AWS team had an internal rollup meeting on Mondays to prepare for Jassy's meeting...
Most of the question mark emails seemed to target more specific issues (mostly customer pain points). The fixers were more for big organisational or tech problems. If your division was significantly behind schedule on a product launch, or your production system had significant failure rates, you were liable to have a Senior Principal engineer and/or a new VP airdropped into your org, with significant leeway to get shit done