What are Microsoft's reasons for developing edge and Bing? Why do they want to compete in those markets?
I'm not sure about Edge entirely, but Microsoft often tries to rebrand its products when those products have a bad reputation in the industry. While I'm not sure if that was the reason, I can also speculate that the code-base for IE was antiquated and convoluted to work with and it made sense to start from scratch.
Initially, Microsoft got into the browser market as there were no web-standards and it was easier for them to push their own products into their own browser via ActiveX controls. In addition, their approach is to be #2 so they can easily replicate what competitors have done and try to make it slightly better in some cases.
As for Bing, Search has been a huge industry worth several hundred billion dollars. There were so many upsides to offering your own search engine. For instance, you could control the content that is displayed. Microsoft could promote its own sites like MSDN and MSN ahead of other online resources. They could accumulate so much data for training machine learning algorithms. If I recall, a 1% market share was worth something like 400 million dollars about ten years ago. It makes for a very good foundation to build other technologies on top.
Besides, the company didn't believe in the future of the internet in the 90's but later started to rush into it once they saw Google and Yahoo's successes.
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