I am convinced by N. T. Wright and others that Jesus is not attacking the temple for financial impropriety. At the same time, economic abuses are certainly part of the evil that Jesus condemns. Jesus final scenes in the temple in Mark are framed by His condemnation of the temple as a “den of brigands” (11:17) and the widow putting her two coins in the temple treasury (12:41-44). Jesus leaves the temple in 13:1, never to return, and describes its destruction in the Olivet Discourse.

The widow is pious, of course, but in context the point of the story is that the temple authorities devour widows’ houses (12:40, just before the scene with the widow). Jesus condemns the temple, among other things, because instead of providing food for widows and orphans (as the festival laws of Deuteronomy require), the temple authorities suck the life from widows, devouring the weak instead of feeding them.