Microsoft's XML office formats were in the 2003 release of Office, which predates ODF's submission to a standards body by a couple of years. A few months later Microsoft's formats were also submitted for standardization.
There were a few reasons the OOXML spec was quite a bit longer than the ODF spec. The main were:
1. ODF has a cleaner and less verbose markup.
2. ODF was very underspecified. For example, the spreadsheet spec didn't say much about formulas beyond that they should exist. The OOXML spec, on the other hand, had hundreds of pages defining spreadsheet formulas and the functions available.
One problem with ODF was that Sun wanted ODF to have just what it needed to support StarOffice and nothing more. There were proposals to make ODF better able to represent documents from other systems such as existing Office, Word Perfect, and Lotus, but Sun had sufficient influence to stop that.
There were a few reasons the OOXML spec was quite a bit longer than the ODF spec. The main were:
1. ODF has a cleaner and less verbose markup.
2. ODF was very underspecified. For example, the spreadsheet spec didn't say much about formulas beyond that they should exist. The OOXML spec, on the other hand, had hundreds of pages defining spreadsheet formulas and the functions available.
One problem with ODF was that Sun wanted ODF to have just what it needed to support StarOffice and nothing more. There were proposals to make ODF better able to represent documents from other systems such as existing Office, Word Perfect, and Lotus, but Sun had sufficient influence to stop that.