This is ultimately a failing of democracy itself. This stuff was legal, and it's hard to make a law that reaches back decades to impose costs on manufacturers or real estate developers without drastic economic side effects. Leaseholders in theory were one of the beneficiaries of the cheap building techniques, but a lot (maybe most?) of the burden of remediation has actually fallen to the taxpayer - typical politicians, winning votes in the 1980s and paying the tax in the 2020s.
Known unsafe building methods should not have been legal, but we know that politicians have been avoiding legislating this specific issue for more 50 years[1]. Politicians need votes or kickbacks in months or a few years at most. Fire safety is a long term investment against a rare problem. Long term investments against even common problems are basically impossible in modern democracies. For example, if you legislate cycle path networks everywhere people will eventually love them and fight to keep them, in addition to delivering economic and health benefits, but outside the Netherlands very few places do it - because it took 40 years in the Netherlands.
[1]