Attiny85 crashes when I run a motor through an L293D
You have no decoupling capacitors.

You need decoupling capacitors because whenever the ICs switch they will try to draw a surge of current. The power supply can't respond fast enough and even if it does, the current surge will produce a voltage drop through the parasitic inductance of the wires and traces. Either scenario will cause a brownout.

The rule of thumb is to place 0.1uF ceramic capacitors across every pair of power pins as close to the IC as possible.