I’m going to keep this one brief.
At the start, Covid could have been stopped with travel bans, track and trace, mandatory isolation and lockdowns.
The problem with how everyone did lockdowns is that they did them too late. Instead of starting lockdowns when hardly anyone had Covid BUT R was over 0 (one case of Covid was spreading to more than one person) they would wait until the numbers were high. As a result lockdowns were long, but never actually crushed Covid and over time support for lockdowns was lost.
But the real problem is that controlling Covid spread required travel bans. Western Australia, which controlled Covid almost completely for over a year, did so by shutting down all non-essential travel. If this had been done worldwide, Covid could have been ended early.