'Howbeit with most of them God was not well pleased, for they were overthrown in the wilderness.'
The spiritual benefits of the Israelites proved to be of no efficacy to them when it came to the sins of idolatry and sexual misbehaviour, both prominent in idol temples. They failed, displeased God and were overthrown in the wilderness one by one as they died off (Numbers 14:16 LXX). Their participation in sacraments had not saved them. Let the Corinthians beware lest the same thing happen to them. Note the 'most of them' taken along with the earlier 'all'. There were only a few of all the adults who originally received the spiritual sacraments who actually survived the stay at Kadesh, e.g. Moses, Caleb and Joshua.
So among these who had experienced these things some were specifically destroyed. Others died one by one, day by day, in the wilderness, their bodies left there in the wilderness. But only the few survived to enter Canaan. We may possibly (and rightly) distinguish between those who were finally lost, those who were saved but did not receive the prize, and those whose triumph was final, but that is not Paul's emphasis here. He is concentrating on the thought of their failure to receive the prize they were aiming at. The point is that they just did not get there. (Aaron fell in the wilderness but we are not to gather from that that God had eternally rejected him. It was simply that he came short of receiving the fullness of blessing).
This is now followed by four or five examples of the way in which the majority had failed. Lusting after evil things; its resultant idolatry, having in mind the molten calf incident when the 'play' probably included sexual misbehaviour as well as false worship (Exodus 32:6); fornication (Numbers 25:1-9); testing God through unbelief (Numbers 21:4-9); murmuring (Numbers 11:1-15). All these sins were being reproduced among the Corinthians.