Unclear what they mean about a second wave. The Mycenaeans most assuredly reached Crete.
The Mycenaeans were the Greek-speaking coat of paint as it were over a number of other related peoples in (mostly western) Anatolia, Greece, and tghe Aegean. As everywhere else in those areas where the Minoans had been found either as residents or as maritime traders, the Mycenaeans took over.
And before anyone brings it up, no, it had nothing to do with Thera.
They couldn’t reach Crete cos it was already inhabited by millions of crawling
cretins.
Yes, if they could reach Troy, which they did, they could reach Crete.
A wave is when a group of people are pushed out of their home area when severe conditions or invasion by a stronger group force them or make it desirable to move elsewhere. We had a wave of Europeans in the 1840s as a result of potato blight in Ireland. Then another in the 1880’s after various social upheavals and struggles in Europe. My mother’s parents came as a result of that one. So the first wave apparently reached Crete, but the second wave did not. There were probably enough genetic differences to determine which ones reached Crete and which did not.