> Why would they do this?
Raw logs are an input; it drives up the price for external industries dependent on lumber and drives them down for domestic industries, sacrificing raw material exports for more competitive intermediate and finished goods exports.
Since for the most part economic development depends on having exports as far toward the finished goods end of the raw material to finished goods spectrum, its not an insane strategy if you can deal with the short-term dislocations.
Shifting competitive advantage is harder than leaning in to your existing competitive advantage, but sometimes your existing competitive advantage is a long-term loser.