This is a common mechanism that powers conspiracy theories: when you see an opportunist profiting from a situation, you may be tempted to conclude that they had to do shaping the situation in their favour, especially if these actors are a group of wealthy connected people. The police/justice system also uses "motive" as a strong requisite for bringing suspicion on a person; it's a quite engrained psychological mechanism (and often fits reality quite well, until it doesn't)