With a two hour limit on debate, multiple challenges could run out the clock and throw the decision to the House where each state has one vote. You are correct that the initial debate in the House would never provide President Trump a path to victory but the object is not to win but just delay until Jan 20.
O Lord, Give Me Strength...
Did any of you actually pay attention in your US Civics class? If there is a successful challenge of an elector or a slate of electors, each house convenes separately to deliberate. THAT deliberation shall last for no more than 2 hours. It doesn’t mean that any and all objections aare allotted in aggregate only 2 hours.