For those who don't understand what I mean, Bryan (D) was a great speaker of his time, tied the Bible and politics together seamlessly in his speeches, and was known to even get the little old ladies riled up with his speeches. His speech "Cross of Gold" is known by some as one of the greatest speeches ever.
On the other hand, McKinley (R) only had a picture of himself with the word "Prosperity" at the top of it. He didn't campaign. He didn't even answer questions of what he was running for. In fact, he didn't even talk to reporters or anything like that.
How could McKinley win with such a large margin with almost nothing as a campaign?
Perhaps someone can give a more thorough answer, but I think your description contains a lot of inaccuracies which might underlie your confusion.
Regardless of how much in person campaigning McKinley did there was still a quite robust, well-funded, and highly effective campaign to elect him. The Republican National Committee put forth a campaign organized at a national level to support McKinley as well as to discredit Bryan and his policies. Indeed, the McKinley campaign pioneered modern campaign financing (compared to the traditional government office kick-back financing of the past), which funded extensive rallies, parades, and pamphlets.
Few reasons why, which may be interesting.
There was a very, very large controversy over McKinley's spending in the campaign. In fact, Illinois Governor John Altgeld and William Jennings Bryan even claimed that McKinley bought the campaign with the help of his wealthy campaign manager, Mark Hanna. It's been estimated that between 13-16 million dollars were spent by Hanna in the effort to get McKinley elected: no small sum by any means. Some estimates go as low as 3 million dollars. We may never know the truth of the matter, but we do know that campaign expenditures were huge on the part of McKinley, which may have given him an advantage in the election since he outspent the Democrats by a very large amount. The lower end near $3 million seem to be the accepted estimates, just as a brief note on that.
McKinley had the benefit of credentials and background working for him, especially in key states like Illinois, and was supported by figures like the fairly wealthy (having inherited some $250,000 worth of property) banker/lawyer Charles G. Dawes. McKinley had been governor of Ohio, lacked any real enemies, and had served in Congress. Bland but safe, he also was viewed as a way out of the ongoing recession. As Pixton puts it, "The Democrats had tinkered with the tariff; hard times had followed; obviously the cure was a return to protection...".
McKinley also was granted a boon by Bryan's campaign tactics. According to Frederick Jackson Turner in The Significance of Sections in American History:
When Bryan in 1896 made his definition of the business man to include the farmer and the miner, and in the Democratic convention of that memorable year 'defied' the East and issued a declaration of rural independence, he made himself the spokesman of a new Democratic problem based on an alliance of West and South."
Robert Kelley expanded on the consequences of this in 1977:
New England had always distrusted both the South and the West; inflationism ran directly against the interests of the consuming masses in the Northeastern and Middle Western cities; the ethnic minorities distrusted Bryan's piety and agrarianism; and in consequence the Democratic party, which formerly had been strong in the Northeast and Middle West, shriveled in those regions. Urban ethnic groups surged toward the Republicans, who during the depression preached even more enthusiastically their traditional message that the government should actively intervene in and stimulate the economy.
So you had a case of Bryan alienating, by his fervor, some of the core key constituencies that his party had traditionally relied on. Such a move changed the way his campaign could win, forcing it to rely on different groups who might not switch to supporting him all too quickly, while he alienated many of his fundraising sources in the Northeast and Midwest.
Altogether, these factors led to Bryan losing the election to the better-run campaign of McKinley, even with McKinley's seemingly bland and (by some accounts) spineless personality. I'm sure there are more factors, but these are the major ones I've heard :).
Sources:
A Short Note on the Expenditures of the McKinley Campaign of 1896 D. Aaron Chandler Presidential Studies Quarterly, Vol. 28, No. 1, Wheeling and Dealing in the White House (Winter, 1998), pp. 88-91
The 1896 Election and Congressional Modernization: An Appraisal of the Evidence Joel Budgor, Elizabeth A. Capell, David A. Flanders, Nelson W. Polsby, Mark C. Westlye and John Zaller Social Science History, Vol. 5, No. 1 (Winter, 1981), pp. 53-90
Charles G. Dawes and the Mckinley Campaign John E. Pixton, Jr. Journal of the Illinois State Historical Society (1908-1984), Vol. 48, No. 3 (Autumn, 1955), pp. 283-306
There are several excellent answers already to this post. I just want to point out, McKinley did talk to reporters, provided they went to his house. His whole campaign was called the Front Porch campaign because it seemed that McKinley did not leave his front porch at all during that campaign. The William McKinley Home and Research Center in Niles Ohio still has the wicker porch furniture and the lemonade pitcher he used during the 1896 campaign, in their museum.