The reason that a larger number of hardware startups have recently appeared is quite simple - these are mostly actually software companies. Modern hardware that a startup might produce - IoT stuff, small computers etc - are essentially bare-minimum hardware wrappers around black-box chips.
The complexity of developing hardware is driven by the number of discrete components used. Every additional resistor is a resistor which can be fitted wrong. Every additional analogue circuit built using discrete components is a huge risk. To build cheap hardware, you avoid all that as much as possible by building PCBs which just wire up highly functional ICs.
In essence your hardware company then becomes a software company.
The complexity of developing hardware is driven by the number of discrete components used. Every additional resistor is a resistor which can be fitted wrong. Every additional analogue circuit built using discrete components is a huge risk. To build cheap hardware, you avoid all that as much as possible by building PCBs which just wire up highly functional ICs.
In essence your hardware company then becomes a software company.