Understanding peak repetitive surge current
That device is not suitable to drive load, it can be used as another triac driver. 1 Amp is can be conducting for short time. That parameter gives you way to calculate resistor between output optotriac MOC3021 and triac gate. In case the triac turned on on voltage peak. For instance, triac commutate 220V, the peak is 315 V. Resistor min 330 Ohm( closest value). When triac on, MOC3021 output is shortened, so current run for short time. The chip body can dissipate only 300 mW, voltage drop on triac 1.7V,so 1 Amps is too much.