If a hardware failure causes downtime you're doing it wrong. Additionally, big cloud scaring people from hardware with marketing and FUD has been very effective. Modern hardware is insanely reliable and performant - I don't think I've seen a datacenter/enterprise NVMe drive fail yet. It's not 2005 with spinning disks and power supplies blowing up left and right anymore.
> With 1 person that person will sometimes be on vacation when a zero day takes you down. With 2 people 1 will be on vacation when the second gets sick. You end up needing at least 5 people before you have enough people that you have redundancy for humans issues and the ability to train people in whatever is the latest needed.
Hardware vendors (Dell, etc) have highly-discounted warranty services. In the event of a hardware failure you open a ticket and they dispatch someone directly to the facility (often within hours by SLA) and it gets handled.
Same thing for shipping HW directly to co-lo and they rack/cable/bootstrap for a nominal fee, remote hands for weird edge-cases, etc.
A lot of takes here and elsewhere seem to be either big-cloud or Meta-level datacenter. I have operated POPs in a dozen co-location ("datacenter") facilities (a cabinet or two each) no one on staff ever stepped foot in with hardware we owned (and/or financed) that no one ever saw or touched. We operated this with two people looking after it as part of their broader roles and responsibilities and frankly they didn't have much to do.
There is an entire industry that provides any number of highly flexible and cost-effective approaches for everything in between.