That's because the final l a dark l /ɫ/.
When the diphthongs aɪ, eɪ or ɔɪ or the vowel /i/ precede a dark l, a schwa can be heard in between. That's why while can sound like /waɪəɫ/, oil like /ɔɪəɫ/, fail like /feɪəl/ and real /riəl/. This should occur naturally, to some extent, if you're pronouncing the dark l correctly.
Additionally, some speakers merge the diphthong with the schwa when using /eɪ/, so that fail sounds more like /feəl/. That can also occur with /aɪ/ that becomes /ɑ:/ in dialectal speech.
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