As you've said, your friend already had an experience investing in altcoins and unfortunately the two alts didn't go well. What's his reaction after knowing the result? Did he blame the one who convinced him to invest? If no, then I will help him to invest if he is interested.

Well, for me, since he already experienced investing in crypto before and likely aware of the risk especially if you happen to choose a wrong coins, then I will encourage him to why not choose Bitcoin this time. It is risky as well but compared to investing in alts, we know Bitcoin is way better and ideal for long term hodling. The good thing about this is, he is not a newbie that is clueless about crypto investment. Educate him further then let him decide on his own.