If not easily avoidable, Kinnock could at the very least made the race competitive. He could have neutralized the attacks on Labour's fully justified antinuclear position(in 1987, Gorbachev was running the USSR, which meant the Cold War was over)by actually spending some time DEFENDING that position and making a coherent, unapologetic case for peace and international reconciliation and the good those things could do for the people of Britain.
Rather than that, all he had done since winning the leadership was to endlessly defer to Matron in question period and attack his own party's supporters rather than the Tories.
It truly looks as though Kinnock deliberately lost the 1987 election badly just to set up the expulsion of anyone who actually supported socialism(he spent the post-87 period doing nothing but endlessly moving Labour policies further and further and further to the right, agreeing to no further nationalization(thus making anything socialist impossible)endorsing Thather's antiworker laws(thus making it impossible for the unions ever to defend their workers from capitalist attack), endorsing the Bomb in an era when there was no longer any good reason for it, and sucking up to the "put the boot in" crowd on crime(thus making it impossible for civil liberties to survive in a Kinnock government).
He'd have been slightly better than Major in '92, but there was no longer anything transformative or even hopeful in the Labour program by then. He lost that election because people wouldn't trust anyone who gave up all his core values just for power in name.
As the Blair years proved, power gained by mass abandonment of principle is meaningless.