why did manitoba join confederation?

Answer 1

The early manitoba economy was one that depended on mobility and living off of the land.
The first major diversification of the economy came when Lord Selkirk first introduced agricultural settlers in the area just north of present day Winnipeg in 1811.
The eventual triumph of the Hudson Bay Company (HBC) over its competitors monoplised the fur trade
a court battle insuded with others because of the monoply.

The republic never had clearly defined borders, and could not persuade local HBC traders to pay their taxes. By spring 1868, the Republic was informed by the Colonial Office in London that its government had no power. The Republic's problems were compounded by misappropriation of tax funds, and a botched treason trial. The Republic of Manitobah collapsed before it had a chance to blossom.

The courts could no longer be used by the HBC to enforce its monopoly. The result was a weakening of HBC rule over the region and laid the foundations of provincehood for Manitoba.
THe Provisional Government, actions led to the formation of the Province of Manitoba within Canada on May 12, 1870.