Well, besides the obvious of paying off mortgages and debts which wouldn't even amount to a fraction of that, I'd buy an island to convert into a 24/7 mass paintball (or laser tag or something) warzone experience, like hundreds of people on both sides.
Sell the experience to people, classic Red team vs blue team, stay until you're eliminated, barracks/camps, HQ, command structures, etc. It would be a live streamed competition with commentary, tactics, live go pro cams, everything. Maybe do it in seasons, have leaderboards, MVPs, whatever.
Players that have already been to the island before would be able to advise, or place bets on their accounts or whatever to build up load outs for their next trip.
The goal being a fun live game, exercise, stamina training, whatever, but mostly an outlet for the people in the world that get excited by war with the intention of hopefully reducing that with a safe environment.
I feel like if done correctly, and made as affordable as possible, it could turn into a relatively profitable business. I would then ensure the profits went to charities that provide aid to actual warzones and ensure that the primary message of the theme park is completely anti-war.
Any money leftover that didn't go into that project I would donate and invest in animal welfare and conservation, renewable energy, and tackling the climate crisis.
This isn't technically the trolly problem, sorry to be pedantic. But the trolly problem is not in the deaths either track would cause, but in the decision to actively pull the lever and make yourself responsible for the outcome. Inaction means allowing what will be to be.
Eg, if the train is heading towards three people, and you can pull the lever to send it towards one, congratulations, you saved two lives. BUT you just made yourself responsible for the murder of one. Whereas before, you would not have been responsible for the death of the three.
Doesn't matter how dressed up the problem is, involvement means making yourself responsible for murder.