The prayer promise is couched in the destruction-of-temple context because Jesus is inaugurating NEW COVENANT prayer — from temple-mediated access to direct access through Christ. Christians ARE the new temple.

In 2 Chronicles 6:24-40, Solomon's temple dedication prayer establishes that Israel accesses God THROUGH the temple — every prayer is directed toward/through it. When the temple was destroyed in 70 AD, rabbis in the Talmud debated whether prayer was even possible anymore. Rabbi Eleazar: "From the day the temple was destroyed, the gates of prayer have been closed" and "a wall of iron divides between Israel and their Father in heaven." This is why Jesus gives a bold prayer promise RIGHT AFTER predicting temple destruction — he's inaugurating the new covenant of prayer. Christians ARE the temple: 1 Peter 2:5 (living stones, spiritual house), Ephesians 2:19-22 (built on Christ the cornerstone, growing into a holy temple), John 4:21-24 ("neither on this mountain nor in Jerusalem will you worship"). "The Jerusalem temple is condemned and replaced by the praying community" (commentator). The simple point for believers: you have direct access to God through Christ — no temple needed.