I think it's the combination of befuddling profligate spending coupled with a rather sub-standard product despite the hundreds of millions of $ thrown at its development and marketing. In short, very poor and perplexing business decisions.

Bear in mind that Shopee has little economic moat and seems to hv no realistic path to profitability. It's really this ONE single product that they have. And SEA burns a lot of cash from their other profitable division, garena, so subsidize this cash burning business.