Interrupt and delay problems on Attiny 85
In short:


Arduino delay() is relying on millis().
The millis() function is  updated by timer ISR.
ISR handler blocks all other ISRs by disabling global interrupts.
No update for millis results into deadlock in delay if you use it in another ISR


And recommendation for ISRs? Do it as short as possible! Set some volatile flag and do the action later outside of ISR.