Bread predates the domestication of wheat. One difficulty with unravelling the history of bread is that bread doesn't preserve well in the archaeological record - the oldest bread that has been found is only a little over 14,000 years old, and the oldest grindstones that we know were used for grinding cereals (possibly for bread, but possibly for other purposes) somewhat over 30,000 years old. There are much older grindstones, and grinding cereals and making bread could be much older.

For hard seeds, and other hard plant foods, crushing or grinding them to make them easier to eat is a logical enough step - not that far removed from opening shellfish, nuts, bones, etc. to get at the tasty softer bits inside.

As for motivation for domesticating wheat, the harvesting of wild wheat for breadmaking is certainly a possible motivation. Wild wheat was being harvested and ground, and bread being made from it in the area where wheat was domesticated. It's quite possible that wheat would have still been domesticated even if it was being consumed in forms other than bread. Te alternative suggestion is that the domestication of wheat (and other cereals) might have been beer-making. This is an old suggestion, and more recent research shows that it is plausible, with evidence of beer-making from about 13,000 years ago, preceding the domestication of wheat.

For more on the history of bread:

• https://www.reddit.com/r/AskHistorians/comments/bvwm17/why_did_ancient_man_create_bread_as_opposed_to/

On bread, wheat, and ancient beer:

• Solomon H. Katz, Mary M. Voigt, "Bread and Beer", Expedition Magazine 28(2), 23-34 (1986). http://www.penn.museum/sites/expedition/?p=5999

• Li Liu, Jiajing Wang, Danny Rosenberg, Hao Zhao, György Lengyel, Dani Nadel, "Fermented beverage and food storage in 13,000 y-old stone mortars at Raqefet Cave, Israel: Investigating Natufian ritual feasting", Journal of Archaeological Science: Reports 21, 783-793 (2018). https://doi.org/10.1016/j.jasrep.2018.08.008