I suspect there was a little rope-a-dope going on on his part. Microsoft was less than a year in to turning their ship around (https://www.wired.com/2010/05/0526bill-gates-internet-memo/) to ride the Internet wave. So he wouldn't have wanted to telegraph to other large competitors that this was going to be huge. (hopefully, given their investments) They already had their hands full with all the tiny startups who had been there years earlier.