Most importantly, back in the day 1998/1999 there was not much around that could match up to the functionality of PHP. Java servlets were not supported widely,

Most importantly, back in the day 1998/1999 there was not much around that could match up to the functionality of PHP. Java servlets were not supported widely, Netscape had their serverside javascript wich required you to buy into their servers... Going with PHP was a no-brainer for any small web-shop/startup. With all the web stacks that are available today, it wouldn't have been that clear.