Just because a company makes bad business decisions doesn't make it OK to screw over customers. Especially with something that costs them very little to operate.
Many "lifetime licenses" are a gamble - you risk the product going away if the company goes bankrupt, and you prepay a lot of money. Granted, here, it was relatively cheap, but that doesn't make it OK to revoke it.
Especially since this seems to be a pure money-grab ("we know you already paid, but how about paying a second time?"), not a "company can't afford the burden of legacy customers given a good deal".
Many "lifetime licenses" are a gamble - you risk the product going away if the company goes bankrupt, and you prepay a lot of money. Granted, here, it was relatively cheap, but that doesn't make it OK to revoke it.
Especially since this seems to be a pure money-grab ("we know you already paid, but how about paying a second time?"), not a "company can't afford the burden of legacy customers given a good deal".