911s weren't selling - Porsche had been in decline for years as their one-model line-up was failing to attract new buyers and I believe they were on the verge of a buyout by Volkswagen. The Boxster turned it all around for them, followed by the 996, followed by the Cayenne - and now they are the major shareholder in Volkswagen!
Porsche Sales: 1994-2004
1994 - 21,124
1995 - 19,262
1996 - 32,383 (Boxster released)
1997 - 36,686
1998 - 43,982 (996 911 released)
1999 - 48,797
2000 - 54,586
2001 - 54,234
2002 - 66,803 (Cayenne released)
2003 - 76,827
2004 - 88,379
Porsche had been in the red for each of the three years before the Boxster was launched - and they turned a profit for the 1996 financial year... The Boxster sold out its entire first year production run before it was even launched...
Had the MX-5 not brought open-top to the masses again, the Boxster might never have entered production - never mind the 996 that they were then able to release, or the Cayenne which is one of the most profitable cars ever made (which also means that the MX-5 is responsible for the Cayenne. Bad MX-5! Bad!) and Porsche would no longer exist as an independent entity.