Complex sentence: This decision was met with widespread opposition by supporters of both sides, especially by Caley fans who were confident their club could successfully bid on their own but an amalgamation went ahead with resentment from Caley fans that the club's board had betrayed them.
Split into simpler sentences: This decision was met with widespread opposition by supporters of both sides, especially by Caley fans who were confident their club could successfully bid on their own. However, an amalgamation went ahead leaving deep resentment from Caley fans that the club's board had betrayed them.